|
[[Dosya:Glycolysis1.png|thumb|right|450px|Kullanılan renklerin tanımı: <span style="font-weight: bold;"><span style="color: blue;">enzimler</span>, <span style="color: rgb(219,155,36);">koenzimler</span>, <span style="color: rgb(151,149,45);">substrat isimleri</span>, <span style="color: rgb(227,13,196);">metal iyonları</span>, <span style="color: rgb(128,0,0);"ben oguzhan>inorganik moleküller</span>, <span style="color: red;">inhibisyon (engelleme)</span> ve <span style="color: red;">bağlı fosfat</span>, <span style="color: green;">stimülasyon (uyarı)</span> </span>]]
{{Çeviri yeri|Glycolysis |İngilizce|en}}
'''Glikoliz''', [[glikoz]]un [[Enzim|enzimlerle]] [[pirüvik asit]]e (pirüvat) kadar yıkılması olayıdır. Bütün canlılarda glikoliz reaksiyonları aynı şekilde gerçekleşir. Olaylar için tüm canlılarda aynı enzimler görevlidir. Başlangıçta glikozu aktifleştirmek için 2 ATP harcanır. Reaksiyonlar sırasında 4 ATP oluşturulur. 2 NADH meydana gelir. Oluşan NADH'lar [[oksijenli solunum]]da elektron taşıma sistemine aktarılır ve her birinden üçer ATP elde edilir. [[Oksijensiz solunum]]da ise NADH'lar [[son ürün evresi]]nde tekrar yükseltgenerek bir sonraki glikoliz olayında kullanılır.
[[Dosya:Glikoliz.svg|thumb|right|250px|Glikoliz şeması]]
'''Glikoliz''' [[glikoz]]'u, C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>, [[pirüvat]]'a, CH<sub>3</sub>COCOO<sup>−</sup> + H<sup>+</sup> kadar yıkan [[metabolik yol]]dur. Bu işlem sırasında oluşan serbest enerji, ATP (adenozin trifosfat) ve NADH (indirgenmiş nikotinamid adenin dinükleotit) gibi yüksek enerjili bileşikler oluşturmak üzere kullanılır.
Glikolizde dikkat edilecek noktalardan biri de Fosfofruktokinaz enziminin katalizlediği Fruktoz 1,6 bifosfat'tan Gliseraldehit 3-fosfat ve Dihidroksiaseton fosfat oluşumudur. Zira bu basamak geri dönüşümsüz hız kısıtlayıcı basamak olup insülin,glukagon ve epinefrin hormonlarının kontrolünde aktive veya inaktive olur.
Glikoliz, on tepkime ve on ara bileşik (aşamaların birinde iki ara bileşik oluşur) oluşumundan ibaret kesin bir tepkimeler dizisidir. Ara bileşikler, glikolize giriş noktası sağlarlar. Örnekle, glikoz, fruktoz ve galaktoz gibi çoğu monosakkarit; bu ara bileşiklerden birine çevrilebilir. Bunun yanında ara bileşikler doğrudan işe yarar olabilir. Örnekle, ara bileşiklerden [[dihidroksi aseton fosfat]], doğrudan [[gliserol]]ün yapısında yer aldığından [[yağ]]ları oluşturmada kullanılır.
Pirüvik asitin oluşturulmasına kadar kullanılan substratlar bütün canlılarda aynıdır (bazı [[kemosentetik]]ler hariç). Bu bilgi canlılarda glikoliz reaksiyonlarını kontrol eden kalıtsal yapı ve enzim benzerliğini kanıtlar.
Glikolizin evrensel metabolik yolların ilk örneği olduğu düşünülmektedir. Öyle ki, [[oksijenli solunum|oksijenli]] veya [[oksijensiz solunum]] yapan herhangi bir canlı bu tepkimeleri çeşitli ufak farklılıklarla da olsa gerçekleştirirler. Glikoliz tepkimelerinin bu denli sık görülmesi, bu tepkimenin bilinen en eski metabolik yollardan biri olduğunun ipuçlarını vermektedir.<ref>Romano AH, Conway T. (1996) Evolution of carbohydrate metabolic pathways. ''Res Microbiol.'' 147(6-7):448-55 PMID 9084754</ref>
== Ayrıca bakınız ==
Glikolizin en bilinen türü ''Embden-Meyerhof yolu'' olup, [[Gustav Embden]] ve [[Otto Meyerhof]] ikilisi tarafından keşfedilmiştir. Glikolizde ''[[Entner–Doudoroff yolu]]'' gibi ayrıca başka türler de bulunur. Ancak bu maddede ağırlıklı olarak işlenen tür Embden-Meyerhof yolu üzerinedir.
* [[Oksijensiz solunum]]
** [[Fermantasyon]]
** [[Alkolik fermantasyon]]
** [[Laktik asit fermantasyonu]]
== GenelKaynakça ==
* Lippincott Illustrated Reviews Biochemistry
Glikolizdeki genel tepkimeler aşağıdaki gibidir:
* Harper's Biochemistry
{| align="center" cellspacing=5 style="border: 1px solid #a79c83"
{|
| align="center" bgcolor ="lightgreen" | <small>D</small>-[Glikoz]
|
|
|
| align="center" bgcolor ="lightgreen" | [Pirüvat]
|
|-
| align="center" | [[Dosya:D-glucose wpmp.png]]
| align="center" | + 2 [NAD]<sup>+</sup> + 2 [ADP] + 2 [P]<sub>i</sub>
| align="center" | [[Dosya:biochem reaction arrow foward NNNN horiz med.png]]
| align="center" | 2
| align="center" | [[Dosya:Pyruvate2 wpmp.png]]
| align="center" | + 2 [NADH] + 2 H<sup>+</sup> + 2 [ATP] + 2 H<sub>2</sub>O
|}
|}
Bu denklemde sembollerin kullanımı, denklemin [[oksijen]], [[hidrojen]] ve diğer atomlara bağlı olarak dengesiz görünmesine neden olmaktadır. Bu denklemdeki atom dengesi iki fosfat grubu (P<sub>i</sub>) tarafından sağlanmaktadır:<ref name="ImportanceBalance">{{Cite doi|10.1007/s11306-008-0142-2}}</ref>
* her bir grupta toplam iki H<sup>+</sup> sağlamak üzere [[hidrojen fosfat]] anyonunun (HPO<sub>4</sub><sup>2-</sup>) bir formu bulunur.
* her biri ADP molekülüne bağlandığında bir oksijen atomunu serbest bırakır ve toplamda iki oksijen atomu sağlar.
ADP ve ATP arasında farklı olmak üzere yükler denge halindedir. Hücresel alanda ADP'deki tüm üç hidroksi grubu -O<sup>-</sup> ve H<sup>+</sup> bileşenlerine ayrılıarak ADP<sup>3-</sup> oluşumuna zemin hazırlar. Bu iyon, Mg<sup>2+</sup> ile iyonik bağlı olarak bulunmaya meyillidir. ATP behaves identically except that it has four hydroxy groups, giving ATPMg<sup>2-</sup>. When these differences along with the true charges on the two phosphate groups are considered together, the net charges of -4 on each side are balanced.
== Dış bağlantılar ==
For simple [[Anaerobic respiration|anaerobic]] [[fermentation (biochemistry)|fermentations]], the metabolism of one molecule of glucose to two molecules of pyruvate has a net yield of two molecules of ATP. Most cells will then carry out further reactions to 'repay' the used NAD<sup>+</sup> and produce a final product of [[ethanol]] or [[lactic acid]]. Many bacteria use inorganic compounds as hydrogen acceptors to regenerate the NAD<sup>+</sup>.
[http://www.ufp.pt/~pedros/bq/glycolysis.htm Glikolizin ardındaki kimyasal mantık]
<!-- interwiki -->
Cells performing [[aerobic respiration]] synthesize much more ATP, but not as part of glycolysis. These further aerobic reactions use [[pyruvate]] and NADH '''+''' H<sup>+</sup> from glycolysis. Eukaryotic aerobic respiration produces approximately 34 additional molecules of ATP for each glucose molecule, however most of these are produced by a vastly different mechanism to the [[substrate-level phosphorylation]] in glycolysis.
The lower energy production, per glucose, of anaerobic respiration relative to aerobic respiration, results in greater flux through the pathway under hypoxic (low-oxygen) conditions, unless alternative sources of anaerobically-oxidizable substrates, such as fatty acids, are found.
== Tarihi ==
Bu süreçlere ilişkin ilk çalışmalar 1860 yılında [[Louis Pasteur]]'in fermantasyon için sorumlu mikroorganizmaları keşfetmesiyle başladı.
In 1897 [[Eduard Buchner]] found that ''extracts'' of certain cells can cause fermentation. In 1905 [[Arthur Harden]] and [[William John Young|William Young]] determined that a heat-sensitive high-molecular-weight subcellular fraction (the enzymes) and a heat-insensitive low-molecular-weight cytoplasm fraction (ADP, ATP and NAD<sup>+</sup> and other [[Cofactor (biochemistry)|cofactors]]) are required together for fermentation to proceed. The details of the pathway were eventually determined by 1940, with a major input from [[Otto Meyerhof]] and some years later by [[Luis Leloir]]. The biggest difficulties in determining the intricacies of the pathway were due to the very short lifetime and low steady-state concentrations of the intermediates of the fast glycolytic reactions.
== Reaksiyonların sırası ==
{{Glikoliz}}
=== Hazırlık aşaması ===<!-- Bu kesit [[Hücresel solunum]]'la bağlantılıdır. -->
İlk beş basamak hazırlık aşaması olarak glikozu iki tane üç karbonlu şeker fosfata ([[Fosfogliseraldehit|PGAL]]) dönüştürmek için enerji harcanmasına ilişkin gerçekleşir.
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| Glikolizdeki ilk basamak [[hekzokinaz]] adındaki bir enzim ailesi tarafından gliokzun [[glikoz 6-fosfat]] (G6P) formuna fosforilasyonudur. Bu reaksiyonda ATP harcanır, fakat bu glikoz yoğunluğunun korunmasında rol oynar, "plasma membrane transporter"ları aracılığıyla hücre içine glikozun taşınmasını sürekli kılınır. In addition, it blocks the glucose from leaking out - the cell lacks transporters for G6P. Glucose may alternatively be from the [[phosphorolysis]] or [[hydrolysis]] of intracellular starch or glycogen.
[[Hayvanlar]]da, hekzokinazın [[glikokinaz]] adında bir [[isozyme]]i is also used in the liver, which has a much lower affinity for glucose (K<sub>m</sub> in the vicinity of normal [[glycemia]]), and differs in regulatory properties. The different substrate affinity and alternate regulation of this enzyme are a reflection of the role of the liver in maintaining blood sugar levels.
''Kofaktörler:''
Mg<sup>2+</sup>
| {{Enzimatik Reaksiyon
|foward_enzyme=[[Hekzokinaz]] ('''HK''')<br />''a transferase''
|reverse_enzyme=
|substrate=<small>D</small>-[[Glikoz]] ('''Glc''')
|product=α-<small>D</small>-[[Glikoz-6-fosfat]] ('''G6P''')
|reaction_direction_(forward/reversible/reverse)=forward
|minor_foward_substrate(s)=[[Adenozin trifosfat|ATP]]
|minor_foward_product(s)= H<sup>+</sup> + [[Adenozin difosfat|ADP]]
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=D-glucose wpmp.png
|product_image=Glucose-6-phosphate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
|Sonra G6P [[glikoz fosfat izomeraz]] tarafından [[fruktoz 6-fosfat]]a (F6P) dönüştürüldü. Bu noktada [[fruktoz]] fosforilasyonla glikolitik evreye de girebilir hâle geldi.
The change in structure is an isomerization, in which the G6P has been converted to F6P. The reaction requires an enzyme, phosphohexose isomerase, to proceed. This reaction is freely reversible under normal cell conditions. However, it is often driven forward because of a low concentration of F6P, which is constantly consumed during the next step of glycolysis. Under conditions of high F6P concentration this reaction readily runs in reverse. This phenomenon can be explained through [[Le Chatelier's Principle]].
| {{Enzimatik Reaksiyon
|foward_enzyme=[[Fosfoglikoz izomeraz]]<br />''an [[isomerase]]''
|reverse_enzyme=
|substrate=α-<small>D</small>-[[Glucose 6-phosphate]] ('''G6P''')
|product=β-<small>D</small>-[[Fructose 6-phosphate]] ('''F6P''')
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)=
|minor_foward_product(s)=
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=Glucose-6-phosphate_wpmp.png
|product_image=Fructose-6-phosphate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| The energy expenditure of another ATP in this step is justified in 2 ways: The glycolytic process (up to this step) is now irreversible, and the energy supplied destabilizes the molecule. Because the reaction catalyzed by [[Phosphofructokinase 1]] (PFK-1) is energetically very favorable, it is essentially irreversible, and a different pathway must be used to do the reverse conversion during [[gluconeogenesis]]. This makes the reaction a key regulatory point (see below). This is also the rate limiting step.
The same reaction can also be catalysed by [[pyrophosphate dependent phosphofructokinase]] ('''PFP''' or '''PPi-PFK'''), which is found in most plants, some bacteria, archea and protists but not in animals. This enzyme uses pyrophosphate (PPi) as a phosphate donor instead of ATP. It is a reversible reaction, increasing the flexibility of glycolytic metabolism.<ref>{{cite journal| last = Reeves| first = R. E.| coauthors = South D. J., Blytt H. J. and Warren L. G.| year = 1974| title = Pyrophosphate: D-fructose 6-phosphate 1-phosphotransferase. A new enzyme with the glycolytic function 6-phosphate 1-phosphotransferase| journal = J Biol Chem| volume = 249| pages = 7737–7741| pmid = 4372217| issue = 24}}</ref> A rarer ADP-dependent PFK enzyme variant has been identified in archaean species.<ref>{{cite journal| last = Selig | first = M.| coauthors = Xavier K. B., Santos H. and Schönheit P.| year = 1997| title = Comparative analysis of Embden-Meyerhof and Entner-Doudoroff glycolytic pathways in hyperthermophilic archaea and the bacterium ''Thermotoga''| journal = Arch Microbiol| volume = 167| pages = 217–232| pmid = 9075622| issue = 4}}</ref>
''Cofactors:''
Mg<sup>2+</sup>
| {{Enzymatic Reaction
|foward_enzyme=[[Phosphofructokinase 1|phosphofructokinase]] ('''PFK-1''')<br />''a transferase''
|reverse_enzyme=
|substrate=β-<small>D</small>-[[Fructose 6-phosphate]] ('''F6P''')
|product=β-<small>D</small>-[[Fructose 1,6-bisphosphate]] ('''F1,6BP''')
|reaction_direction_(forward/reversible/reverse)=forward
|minor_foward_substrate(s)= ATP
|minor_foward_product(s)= H<sup>+</sup> + ADP
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=Fructose-6-phosphate_wpmp.png
|product_image=beta-D-fructose-1,6-bisphosphate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| Destabilizing the molecule in the previous reaction allows the hexose ring to be split by [[Aldolase A|aldolase]] into two triose sugars, [[dihydroxyacetone phosphate]], a ketone, and [[glyceraldehyde 3-phosphate]], an aldehyde. There are two classes of aldolases: class I aldolases, present in animals and plants, and class II aldolases which present in fungi and bacteria; the two classes use different mechanisms in cleaving the ketose ring.
| {{ Complex Enzymatic Reaction
|major_substrate_1=β-<small>D</small>-[[Fructose 1,6-bisphosphate]] ('''F1,6BP''')
|major_substrate_1_stoichiometric_constant=
|major_substrate_1_image=beta-D-fructose-1,6-bisphosphate_wpmp.png
|major_substrate_2=
|major_substrate_2_stoichiometric_constant=
|major_substrate_2_image=
|major_product_1=<small>D</small>-[[glyceraldehyde 3-phosphate]] ('''GADP''')
|major_product_1_stoichiometric_constant=
|major_product_1_image=D-glyceraldehyde-3-phosphate wpmp.png
|major_product_2=[[dihydroxyacetone phosphate]] ('''DHAP''')
|major_product_2_stoichiometric_constant=
|major_product_2_image=glycerone-phosphate_wpmp.png
|foward_enzyme=[[fructose bisphosphate aldolase]] ('''ALDO''')<br />''a [[lyase]]''
|reverse_enzyme=
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)=
|minor_foward_product(s)=
|minor_reverse_product(s)=
|minor_reverse_substrate(s)=
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| [[Triosephosphate isomerase]] rapidly interconverts dihydroxyacetone phosphate with [[glyceraldehyde 3-phosphate]] ('''GADP''') that proceeds further into glycolysis. This is advantageous, as it directs dihydroxyacetone phosphate down the same pathway as glyceraldehyde 3-phosphate, simplifying regulation.
| {{Enzymatic Reaction
|foward_enzyme=[[triosephosphate isomerase]] ('''TPI''')<br />''an isomerase''
|reverse_enzyme=
|substrate=[[Dihydroxyacetone phosphate]] ('''DHAP''')
|product=<small>D</small>-[[glyceraldehyde 3-phosphate]] ('''GADP''')
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)=
|minor_foward_product(s)=
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=glycerone-phosphate_wpmp.png
|product_image=D-glyceraldehyde-3-phosphate wpmp.png
}}
|}
===Pay-off phase===<!-- This section is linked from [[Cellular respiration]] -->
The second half of glycolysis is known as the pay-off phase, characterised by a net gain of the energy-rich molecules ATP and NADH. Since glucose leads to two triose sugars in the preparatory phase, each reaction in the pay-off phase occurs twice per glucose molecule. This yields 2 NADH molecules and 4 ATP molecules, leading to a net gain of 2 NADH molecules and 2 ATP molecules from the glycolytic pathway per glucose.
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
|The triose sugars are [[oxidised|dehydrogenated]] and [[inorganic phosphate]] is added to them, forming [[1,3-bisphosphoglycerate]].
The hydrogen is used to reduce two molecules of [[NAD+|NAD<sup>+</sup>]], a hydrogen carrier, to give NADH '''+''' H<sup>+</sup> for each triose.
Hydrogen atom balance and charge balance are both maintained because the phosphate (P<sub>i</sub>) group actually exists in the form of a [[Phosphoric acid#Orthophosphoric acid chemistry|hydrogen phosphate]] anion (HPO<sub>4</sub><sup>2-</sup>)<ref name="ImportanceBalance" /> which dissociates to contribute the extra H<sup>+</sup> ion and gives a net charge of -3 on both sides.
| {{Enzymatic Reaction
|foward_enzyme=[[glyceraldehyde phosphate dehydrogenase]] ('''GAPDH''')<br />''an [[oxidoreductase]]''
|reverse_enzyme=
|substrate=[[glyceraldehyde 3-phosphate]] ('''GADP''')
|product=<small>D</small>-[[1,3-bisphosphoglycerate]] ('''1,3BPG''')
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)=NAD<sup>+</sup> '''+''' P<sub>i</sub>
|minor_foward_product(s)=NADH '''+''' H<sup>+</sup>
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=D-glyceraldehyde-3-phosphate wpmp.png
|product_image=1,3-bisphospho-D-glycerate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| This step is the enzymatic transfer of a phosphate group from [[1,3-bisphosphoglycerate]] to ADP by [[phosphoglycerate kinase]], forming ATP and [[3-phosphoglycerate]]. At this step, glycolysis has reached the break-even point: 2 molecules of ATP were consumed, and 2 new molecules have now been synthesized. This step, one of the two substrate-level phosphorylation steps, requires ADP; thus, when the cell has plenty of ATP (and little ADP), this reaction does not occur. Because ATP decays relatively quickly when it is not metabolized, this is an important regulatory point in the glycolytic pathway.
ADP actually exists as ADPMg<sup>-</sup> and ATP as ATPMg<sup>2-</sup>, balancing the charges at -5 both sides.
''Cofactors:''
Mg<sup>2+</sup>
| {{Enzymatic Reaction
|foward_enzyme=[[phosphoglycerate kinase]] ('''PGK''')<br />''a [[transferase]]''
|reverse_enzyme=[[phosphoglycerate kinase]] ('''PGK''')
|substrate=[[1,3-bisphosphoglycerate]] ('''1,3-BPG''')
|product=[[3-phosphoglycerate]] ('''3-P-G''')
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)= ADP
|minor_foward_product(s)= ATP
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=1,3-bisphospho-D-glycerate_wpmp.png
|product_image=3-phospho-D-glycerate_trulyglycerate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| [[Phosphoglycerate mutase]] now forms [[2-phosphoglycerate]].
| {{Enzymatic Reaction
|foward_enzyme=[[phosphoglycerate mutase]] ('''PGM''')<br />''a [[mutase]]''
|reverse_enzyme=
|substrate=[[3-phosphoglycerate]] ('''3PG''')
|product=[[2-phosphoglycerate]] ('''2PG''')
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)=
|minor_foward_product(s)=
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=3-phospho-D-glycerate_trulyglycerate_wpmp.png
|product_image=2-phospho-D-glycerate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| [[Enolase]] next forms [[phosphoenolpyruvate]] from [[2-phosphoglycerate]].
''Cofactors:''
2 Mg<sup>2+</sup>: one "conformational" ion to coordinate with the carboxylate group of the substrate, and one "catalytic" ion which participates in the dehydration.
| {{Enzymatic Reaction
|foward_enzyme=[[enolase]] ('''ENO''')<br />''a [[lyase]]''
|reverse_enzyme=[[enolase]] ('''ENO''')
|substrate=[[2-phosphoglycerate]] ('''2PG''')
|product=[[phosphoenolpyruvate]] ('''PEP''')
|reaction_direction_(forward/reversible/reverse)=reversible
|minor_foward_substrate(s)=
|minor_foward_product(s)= H<sub>2</sub>O
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=2-phospho-D-glycerate_wpmp.png
|product_image=phosphoenolpyruvate_wpmp.png
}}
|}
<br />
{| cellspacing=15 width=100% style="border: 1px solid #a79c83"
| A final substrate-level phosphorylation now forms a molecule of pyruvate and a molecule of ATP by means of the enzyme [[pyruvate kinase]]. This serves as an additional regulatory step, similar to the phosphoglycerate kinase step.
''Cofactors:''
Mg<sup>2+</sup>
| {{Enzymatic Reaction
|foward_enzyme=[[pyruvate kinase]] ('''PK''')<br />''a transferase''
|reverse_enzyme=
|substrate=[[phosphoenolpyruvate]] ('''PEP''')
|product=[[pyruvate]] ('''Pyr''')
|reaction_direction_(forward/reversible/reverse)=forward
|minor_foward_substrate(s)= ADP + H<sup>+</sup>
|minor_foward_product(s)= ATP
|minor_reverse_substrate(s)=
|minor_reverse_product(s)=
|substrate_image=phosphoenolpyruvate_wpmp.png
|product_image=pyruvate_wpmp.png
}}
|}
== Regulation ==
Glycolysis is regulated by slowing down or speeding up certain steps in the glycolysis pathway. This is accomplished by inhibiting or activating the enzymes that are involved. The steps that are regulated may be determined by calculating the change in free energy, Δ''G'', for each step. If a step's products and reactants are in equilibrium, then the step is assumed to not be regulated. Since the change in free energy is zero for a system at equilibrium, ''any step with a free energy change near zero is not being regulated''. If a step is being regulated, then that step's enzyme is not converting reactants into products as fast as it could, resulting in a build-up of reactants, which would be converted to products if the enzyme were operating faster. Since the reaction is thermodynamically favorable, the change in free energy for the step will be negative. ''A step with a large negative change in free energy is assumed to be regulated.''
=== Free energy changes ===
{| align="right" class="wikitable"
|+Concentrations of metabolites in [[Red blood cell|erythrocytes]]<ref>{{Cite book
| last = Garrett
| first = R.
| last2 = Grisham
| first2 = C. M.
| title = Biochemistry
| place = Belmont, CA
| publisher = Thomson Brooks/Cole
| year = 2005
| volume =
| edition = 3rd
| page = 584
| url =
| doi =
| id =
| isbn = 0-534-49011-6 }}
</ref>
!Compound
!Concentration / m''M''
|-
|glucose
|5.0
|-
|glucose-6-phosphate
|0.083
|-
|fructose-6-phosphate
|0.014
|-
|fructose-1,6-bisphosphate
|0.031
|-
|dihydroxyacetone phosphate
|0.14
|-
|glyceraldehyde-3-phosphate
|0.019
|-
|1,3-bisphosphoglycerate
|0.001
|-
|2,3-bisphosphoglycerate
|4.0
|-
|3-phosphoglycerate
|0.12
|-
|2-phosphoglycerate
|0.03
|-
|phosphoenolpyruvate
|0.023
|-
|pyruvate
|0.051
|-
|ATP
|1.85
|-
|ADP
|0.14
|-
|P<sub>i</sub>
|1.0
|-
|Colspan=2|
[[Image:Glycolysis free energy changes.svg|thumb|center|300px|The change in free energy for each step of glycolysis estimated from the concentration of metabolites in a [[erythrocyte]].]]
|}
The change in free energy, Δ''G'', for each step in the glycolysis pathway can be calculated using Δ''G'' = Δ''G''°' + ''RT''ln ''Q'', where ''Q'' is the [[reaction quotient]]. This requires knowing the concentrations of the [[Metabolomics|metabolites]]. All of these values are available for [[Red blood cell|erythrocytes]], with the exception of the concentrations of NAD<sup>+</sup> and NADH. The ratio of [[NADH|NAD<sup>+</sup> to NADH]] is approximately 1, which results in these concentrations canceling out in the reaction quotient. (Since NAD<sup>+</sup> and NADH occur on opposite sides of the reactions, one will be in the numerator and the other in the denominator.)
Using the measured concentrations of each step, and the standard free energy changes, the actual free energy change can be calculated.
{| class="wikitable"
|+Change in free energy for each step of glycolysis<ref>{{Cite book
| last = Garrett
| first = R.
| last2 = Grisham
| first2 = C. M.
| title = Biochemistry
| place = Belmont, CA
| publisher = Thomson Brooks/Cole
| year = 2005
| volume =
| edition = 3rd
| pages = 582–583
| url =
| doi =
| id =
| isbn = 0-534-49011-6 }}
</ref>
!Step
!Reaction
!Δ''G''°' / (kJ/mol)
!Δ''G'' / (kJ/mol)
|-
| 1
|glucose + ATP<sup>4-</sup> → glucose-6-phosphate<sup>2-</sup> + ADP<sup>3-</sup> + H<sup>+</sup>
| -16.7
| -34
|-
| 2
|glucose-6-phosphate<sup>2-</sup> → fructose-6-phosphate<sup>2-</sup>
|1.67
| -2.9
|-
| 3
|fructose-6-phosphate<sup>2-</sup> + ATP<sup>4-</sup> → fructose-1,6-bisphosphate<sup>4-</sup> + ADP<sup>3-</sup> + H<sup>+</sup>
| -14.2
| -19
|-
| 4
|fructose-1,6-bisphosphate<sup>4-</sup> → dihydroxyacetone phosphate<sup>2-</sup> + glyceraldehyde-3-phosphate<sup>2-</sup>
|23.9
| -0.23
|-
| 5
|dihydroxyacetone phosphate<sup>2-</sup> → glyceraldehyde-3-phosphate<sup>2-</sup>
|7.56
| 2.4
|-
| 6
|glyceraldehyde-3-phosphate<sup>2-</sup> + P<sub>i</sub><sup>2-</sup> + NAD<sup>+</sup> → 1,3-bisphosphoglycerate<sup>4-</sup> + NADH + H<sup>+</sup>
|6.30
| -1.29
|-
| 7
|1,3-bisphosphoglycerate<sup>4-</sup> + ADP<sup>3-</sup> → 3-phosphoglycerate<sup>3-</sup> + ATP<sup>4-</sup>
| -18.9
| 0.09
|-
| 8
|3-phosphoglycerate<sup>3-</sup> → 2-phosphoglycerate<sup>3-</sup>
| 4.4
| 0.83
|-
| 9
|2-phosphoglycerate<sup>3-</sup> → phosphoenolpyruvate<sup>3-</sup> + H<sub>2</sub>O
| 1.8
| 1.1
|-
| 10
|phosphoenolpyruvate<sup>3-</sup> + ADP<sup>3-</sup> + H<sup>+</sup> → pyruvate<sup>-</sup> + ATP<sup>4-</sup>
| -31.7
| -23.0
|-
|}
From measuring the physiological concentrations of metabolites in a erythrocyte it seems that about seven of the steps in glycolysis are in equilibrium for that cell type. Three of the steps—the ones with large negative free energy changes—are not in equilibrium and are referred to as ''irreversible''; such steps are often subject to regulation.
Step 5 in the figure is shown behind the other steps, because that step is a side reaction that can decrease or increase the concentration of the intermediate, glyceraldehyde-3-phosphate. That compound is converted to dihydroxyacetone phosphate by the enzyme, triose phosphate isomerase, which is a [[kinetic perfection|catalytically perfect]] enzyme; its rate is so fast that the reaction can be assumed to be in equilibrium. The fact that Δ''G'' is not zero indicates that the actual concentrations in the erythrocyte are not accurately known.
=== Biochemical logic ===
The existence of more than one point of regulation indicates that intermediates between those points enter and leave the glycolysis pathway by other processes. For example, in the first regulated step, [[hexokinase]] converts glucose into glucose-6-phosphate. Instead of continuing through the glycolysis pathway, this intermediate can be converted into glucose storage molecules, such as [[glycogen]] or [[starch]]. The reverse reaction, breaking down, e.g., glycogen, produces mainly glucose-6-phosphate; very little free glucose is formed in the reaction. The glucose-6-phosphate so produced can enter glycolysis ''after'' the first control point.
In the second regulated step (the third step of glycolysis) [[phosphofructokinase]] converts fructose-6-phosphate into fructose-1,6-bisphosphate, which then is converted into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The dihydroxyacetone phosphate can be removed from glycolysis by conversion into glycerol-3-phosphate, which can be used to form triglycerides.<ref>{{Cite book
| last = Berg
| first = J. M.
| last2 = Tymoczko
| first2 = J. L.
| last3 = Stryer
| first3 = L.
| title = Biochemistry
| place = New York
| publisher = Freeman
| year = 2007
| volume =
| edition = 6th
| page = 622
| url =
| doi =
| id =
| isbn = 0-534-49011-6 }}</ref> Conversely, [[triglyceride]]s can be broken down into fatty acids and glycerol; the latter, in turn, can be [[Glycerol#Metabolism|converted]] into dihydroxyacetone phosphate, which can enter glycolysis ''after'' the second control point.
=== Regulation ===
The three [[enzymes#Control of activity|regulated enzymes]] are [[hexokinase]], [[phosphofructokinase 1|phosphofructokinase]], and [[pyruvate kinase]].
The [[flux (biochemistry)|flux]] through the glycolytic pathway is adjusted in response to conditions both inside and outside the cell. The rate in liver is regulated to meet major cellular needs: (1) the production of ATP, (2) the provision of building blocks for biosynthetic reactions, and (3) to lower blood glucose, one of the major functions of the liver. When blood sugar falls, glycolysis is halted in the liver to allow the reverse process, [[gluconeogenesis]]. In glycolysis, the reactions catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase are effectively [[irreversible]] in most organisms. In metabolic pathways, such [[enzymes#Control of activity|enzymes]] are potential sites of control, and all three enzymes serve this purpose in glycolysis.
==== Hexokinase ====
[[File:Hexokinase B 1IG8 wpmp.png|thumb|right|[[Yeast]] [[hexokinase]] B. {{PDB|1IG8}}.]]
In animals, regulation of blood glucose levels by the liver is a vital part of [[homeostasis]]. In liver cells, extra G6P (glucose-6-phosphate) may be converted to G1P for conversion to [[glycogen]], or it is alternatively converted by glycolysis to [[acetyl-CoA]] and then [[citrate]]. Excess [[citrate]] is exported to the cytosol, where [[ATP citrate lyase]] will regenerate [[acetyl-CoA]] and OAA. The [[acetyl-CoA]] is then used for [[fatty acid synthesis]] and cholesterol synthesis, two important ways of utilizing excess glucose when its concentration is high in blood. Liver contains both [[hexokinase]] and [[glucokinase]]; the latter catalyses the phosphorylation of glucose to G6P and is not inhibited by G6P. Thus it allows glucose to be converted into glycogen, fatty acids, and cholesterol even when hexokinase activity is low.<ref>Voet D., and Voet J. G. (2004). Biochemistry 3rd Edition (New York, John Wiley & Sons,
Inc.)</ref> This is important when blood glucose levels are high. During [[hypoglycemia]], the glycogen can be converted back to G6P and then converted to glucose by a liver-specific enzyme [[glucose 6-phosphatase]]. This reverse reaction is an important role of liver cells to maintain blood sugars levels during fasting. This is critical for brain function, since the brain utilizes glucose as an energy source under most conditions.
==== Phosphofructokinase ====
[[File:Phosphofructokinase 6PFK wpmp.png|thumb|left|[[Bacillus stearothermophilus]] [[phosphofructokinase]]. {{PDB|6PFK}}.]]
[[Phosphofructokinase 1|Phosphofructokinase]] is an important control point in the glycolytic pathway, since it is one of the irreversible steps and has key allosteric effectors, [[Adenosine monophosphate|AMP]] and [[fructose 2,6-bisphosphate]] (F2,6BP).
[[Fructose 2,6-bisphosphate]] (F2,6BP) is a very potent activator of phosphofructokinase (PFK-1) that is synthesised when F6P is phosphorylated by a second phosphofructokinase ([[PFK2]]). In liver, when blood sugar is low and [[glucagon]] elevates cAMP, [[PFK2]] is phosphorylated by protein kinase A. The phosphorylation inactivates [[PFK2]], and another domain on this protein becomes active as [[fructose 2,6-bisphosphatase]], which converts F2,6BP back to F6P. Both [[glucagon]] and [[epinephrine]] cause high levels of cAMP in the liver. The result of lower levels of liver fructose-2,6-bisphosphate is a decrease in activity of [[phosphofructokinase]] and an increase in activity of [[fructose 1,6-bisphosphatase]], so that gluconeogenesis (essentially "glycolysis in reverse") is favored. This is consistent with the role of the liver in such situations, since the response of the liver to these hormones is to release glucose to the blood.
[[Adenosine triphosphate|ATP]] competes with [[Adenosine monophosphate|AMP]] for the allosteric effector site on the PFK enzyme. [[Adenosine triphosphate|ATP]] concentrations in cells are much higher than [[Adenosine monophosphate|AMP]], typically 100-fold higher,<ref>Beis I., and Newsholme E. A. (1975). The contents of adenine nucleotides, phosphagens and some glycolytic intermediates in resting muscles from vertebrates and invertebrates. Biochem J 152, 23-32.</ref> but the concentration of [[Adenosine triphosphate|ATP]] does not change more than about 10% under physiological conditions, whereas a 10% drop in [[Adenosine triphosphate|ATP]] results in a 6-fold increase in [[Adenosine monophosphate|AMP]].<ref>Voet D., and Voet J. G. (2004). Biochemistry 3rd Edition (New York, John Wiley & Sons, Inc.).</ref> Thus, the relevance of [[Adenosine triphosphate|ATP]] as an allosteric effector is questionable. An increase in [[Adenosine monophosphate|AMP]] is a consequence of a decrease in [[energy charge]] in the cell.
[[Citrate]] inhibits phosphofructokinase when tested ''in vitro'' by enhancing the inhibitory effect of ATP. However, it is doubtful that this is a meaningful effect ''in vivo'', because citrate in the cytosol is mainly utilized for conversion to [[acetyl-CoA]] for [[fatty acid]] and [[cholesterol]] synthesis.
==== Pyruvate kinase ====
[[File:Pyruvate Kinase 1A3W wpmp.png|thumb|right|[[Yeast]] [[pyruvate kinase]]. {{PDB|1A3W}}.]]
This enzyme catalyzes the last step of glycolysis, in which pyruvate and ATP are formed. Regulation of this enzyme is discussed in the main topic, [[pyruvate kinase]].
== Post-glycolysis processes ==
The overall process of glycolysis is:
:glucose + 2 NAD<sup>+</sup> + 2 ADP + 2 P<sub>i</sub> → 2 pyruvate + 2 NADH + 2 H<sup>+</sup> + 2 ATP + 2 H<sub>2</sub>O
If glycolysis were to continue indefinitely, all of the NAD<sup>+</sup> would be used up, and glycolysis would stop. To allow glycolysis to continue, organisms must be able to oxidize NADH back to NAD<sup>+</sup>.
=== [[Anaerobic respiration]] ===
One method of doing this is to simply have the pyruvate do the oxidation; in this process the pyruvate is converted to [[lactic acid|lactate]] (the [[conjugate base]] of lactic acid) in a process called [[lactic acid fermentation]]:
:pyruvate + NADH + H<sup>+</sup> → lactate + NAD<sup>+</sup>
This process occurs in the [[bacterium|bacteria]] involved in making [[yogurt]] (the lactic acid causes the milk to curdle). This process also occurs in animals under hypoxic (or partially-anaerobic) conditions, found, for example, in overworked muscles that are starved of oxygen, or in infarcted heart muscle cells. In many tissues, this is a cellular last resort for energy; most animal tissue cannot maintain anaerobic respiration for an extended length of time.
Some organisms, such as yeast, convert NADH back to NAD<sup>+</sup> in a process called [[ethanol fermentation]]. In this process the pyruvate is converted first to acetaldehyde and carbon dioxide, then to ethanol.
[[Lactic acid fermentation]] and [[ethanol fermentation]] can occur in the absence of oxygen. This anaerobic fermentation allows many single-celled organisms to use glycolysis as their only energy source.
In the above two examples of fermentation, NADH is oxidized by transferring two electrons to pyruvate. However, anaerobic bacteria use a wide variety of compounds as the terminal electron acceptors in [[cellular respiration]]: nitrogenous compounds, such as nitrates and nitrites; sulfur compounds, such as sulfates, sulfites, sulfur dioxide, and elemental sulfur; carbon dioxide; iron compounds; manganese compounds; cobalt compounds; and uranium compounds.
=== [[Aerobic respiration]] ===
In [[aerobic organism]]s, a complex mechanism has evolved to use the oxygen in air as the final electron acceptor of respiration.
* First, pyruvate is converted to [[acetyl-CoA]] and CO<sub>2</sub> within the [[mitochondria]] in a process called [[pyruvate decarboxylation]].
* Second, the acetyl-CoA enters the [[citric acid cycle]], where it is fully oxidized to carbon dioxide and [[water]], producing yet more NADH.
* Third, the NADH is oxidized to NAD<sup>+</sup> by the [[electron transport chain]], using oxygen as the final electron acceptor. This process creates a "hydrogen ion gradient" across the inner membrane of the mitochondria.
* Fourth, the proton gradient is used to produce a large amount of ATP in a process called [[oxidative phosphorylation]].
=== Intermediates for other pathways ===
This article concentrates on the [[catabolic]] role of glycolysis with regard to converting potential chemical energy to usable chemical energy during the oxidation of glucose to pyruvate. However, many of the metabolites in the glycolytic pathway are also used by [[anabolic]] pathways, and, as a consequence, flux through the pathway is critical to maintain a supply of carbon skeletons for biosynthesis.
In addition, not all carbon entering the pathway leaves as pyruvate and may be extracted at earlier stages to provide carbon compounds for other pathways.
These metabolic pathways are all strongly reliant on glycolysis as a source of metabolites:
* [[Gluconeogenesis]]
* [[Lipid metabolism]]
* [[Pentose phosphate pathway]]
* [[Citric acid cycle]], which in turn leads to:
:*[[Amino acid synthesis]]
:*[[Nucleotide#Synthesis|Nucleotide synthesis]]
:*[[Porphyrin#Biosynthesis|Tetrapyrrole synthesis]]
From an [[anabolism|anabolic]] metabolism perspective, the NADH has a role to drive synthetic reactions, doing so by directly or indirectly reducing the pool of NADP+ in the cell to NADPH, which is another important reducing agent for biosynthetic pathways in a cell.
== Glycolysis in disease ==
=== Genetic diseases ===
Glycolytic mutations are generally rare due to importance of the metabolic pathway, this means that the majority of occurring mutations result in an inability for the cell to respire, and therefore cause the death of the cell at an early stage. However some mutations are seen.
{{Expand-section|date=June 2008}}
=== Cancer ===
Malignant rapidly-growing [[tumor]] cells typically have glycolytic rates that are up to 200 times higher than those of their normal tissues of origin. There are two common explanations. The classical explanation is that there is poor blood supply to tumors causing local depletion of oxygen. There is also evidence that attributes some of these high aerobic glycolytic rates to an overexpressed form of mitochondrially-bound [[hexokinase]]<ref>{{cite web | title=High Aerobic Glycolysis of Rat Hepatoma Cells in Culture: Role of Mitochondrial Hexokinase -- Bustamante and Pedersen 74 (9): 3735 -- Proceedings of the National Academy of Sciences | url=http://www.pnas.org/cgi/reprint/74/9/3735 | dateformat=mdy | accessdate=December 5 2005 }}</ref> responsible for driving the high glycolytic activity. This phenomenon was first described in 1930 by [[Otto Warburg]], and hence it is referred to as the [[Warburg effect]]. [[Warburg hypothesis]] claims that cancer is primarily caused by dysfunctionality in mitochondrial metabolism, rather than because of uncontrolled growth of cells. There is ongoing research to affect mitochondrial metabolism and treat cancer by starving cancerous cells in various new ways, including a [[ketogenic diet]].
This high glycolysis rate has important medical applications, as high aerobic glycolysis by malignant tumors is utilized clinically to diagnose and monitor treatment responses of [[cancers]] by [[Chemical imaging|imaging]] uptake of [[Fluorodeoxyglucose|2-<sup>18</sup>F-2-deoxyglucose]] (FDG) (a [[radioactive]] modified hexokinase [[substrate (biochemistry)|substrate]]) with [[positron emission tomography]] (PET).<ref>{{cite web | title=PET Scan: PET Scan Info Reveals ... | url=http://www.petscaninfo.com/ | dateformat=mdy | accessdate=December 5 2005 }}</ref><ref>{{cite web | title=4320139 549..559 | url=http://biogenomica.com/PDFs/PauwelsPETandHexokinase.pdf | dateformat=mdy | accessdate=December 5 2005 }}</ref>
=== Alzheimer's disease ===
Disfunctioning glycolysis or glucose metabolism in fronto-temporo-parietal and cingulate cortices has been associated with [[Alzheimer's disease]] <ref name=rcgm>{{cite journal
| last = Hunt
| first = A . ''et al.''
| authorlink =
| coauthors =
| title = Reduced cerebral glucose metabolism in patients at risk for Alzheimer's disease
| journal = Psychiatry Research: Neuroimaging
| volume = 155
| issue = 2
| pages = 147–154
| publisher =
| date = 2007
| url =
| doi = 10.1016/j.pscychresns.2006.12.003
| accessdate =
| accessyear =
| last2 = Schonknecht
| first2 = P
| last3 = Henze
| first3 = M
| last4 = Seidl
| first4 = U
| last5 = Haberkorn
| first5 = U
| last6 = Schroder
| first6 = J }}</ref>, probably due to the decreased [[beta-amyloid|amyloid β (1-42)]] (Aβ42) and increased [[Tau protein|tau]], phosphorylated tau in [[cerebrospinal fluid]] (CSF) <ref name=cmmi>{{cite journal
| last = Hunt
| first = A . ''et al.''
| authorlink =
| coauthors =
| title = CSF and MRI markers independently contribute to the diagnosis of Alzheimer's disease
| journal = Neurobiology of Aging
| volume = 29
| issue = 5
| pages = 669–675
| publisher =
| date = 2008
| url =
| doi = 10.1016/j.neurobiolaging.2006.11.018
| accessdate =
| accessyear =
| pmid = 17208336
| last2 = Van Der Flier
| first2 = WM
| last3 = Blankenstein
| first3 = MA
| last4 = Bouwman
| first4 = FH
| last5 = Van Kamp
| first5 = GJ
| last6 = Barkhof
| first6 = F
| last7 = Scheltens
| first7 = P }}</ref>
== Alternative nomenclature ==
Some of the metabolites in glycolysis have alternative names and nomenclature. In part, this is because some of them are common to other pathways, such as the [[Calvin cycle]].
{| class="wikitable"
!
!colspan="2"|This article
!Alternative names
!Alternative nomenclature
|-
|1
|[[glucose]]
|'''Glc'''
|dextrose
|
|-
|3
|[[fructose 6-phosphate]]
|'''F6P'''
|
|
|-
|4
| [[fructose 1,6-bisphosphate]]
|'''F1,6BP'''
|fructose 1,6-diphosphate
|'''FBP''', '''FDP''', '''F1,6DP'''
|-
|5
|[[dihydroxyacetone phosphate]]
|'''DHAP'''
|glycerone phosphate
|
|-
|6
|[[glyceraldehyde 3-phosphate]]
|'''GADP'''
|3-phosphoglyceraldehyde
|'''PGAL''', '''G3P''', '''GALP''','''GAP''','''TP'''
|-
|7
| [[1,3-bisphosphoglycerate]]
|'''1,3BPG'''
|glycerate 1,3-bisphosphate,<br />glycerate 1,3-diphosphate,<br />1,3-diphosphoglycerate
|'''PGAP''', '''BPG''', '''DPG'''
|-
|8
|[[3-phosphoglycerate]]
|'''3PG'''
|glycerate 3-phosphate
|'''PGA''', '''GP'''
|-
|9
| [[2-phosphoglycerate]]
|'''2PG'''
|glycerate 2-phosphate
|
|-
|10
|[[phosphoenolpyruvate]]
|'''PEP'''
|
|
|-
|11
| [[pyruvate]]
|'''Pyr'''
|pyruvic acid
|
|-
|}
== Ayrıca Bakınız ==
* [[Pentose phosphate pathway]]
* [[Gluconeogenesis]]
* [[Fermentation (biochemistry)]]
* [[Pyruvate decarboxylation]]
* [[Citric acid cycle]]
* [[Triose kinase]]
* [[carbohydrate catabolism]]
* [[Cori cycle]]
== References ==
{{reflist|2}}
== External links ==
* [http://www.1lec.com/Biochemistry/How%20Glycolysis%20Work/index.html A Simplified Glycolysis Animation] ([http://get.adobe.com/flashplayer/ Adobe Flash] Required)
*[http://www.iubmb-nicholson.org/swf/glycolysis.swf A Detailed Glycolysis Animation provided by [[IUBMB]]] ([http://get.adobe.com/flashplayer/ Adobe Flash] Required)
* [http://nist.rcsb.org/pdb/molecules/pdb50_1.html The Glycolytic enzymes in Glycolysis] at [[Protein Data Bank]]
* [http://www.wdv.com/CellWorld/Biochemistry/Glycolytic Glycolytic cycle with animations] at wdv.com
* [http://www.biochemweb.org/metabolism.shtml Metabolism, Cellular Respiration and Photosynthesis - The Virtual Library of Biochemistry and Cell Biology] at biochemweb.org
* [http://www.rahulgladwin.com/blog/2007/01/notes-on-glycolysis.html notes on glycolysis] at rahulgladwin.com
* [http://www2.ufp.pt/~pedros/bq/glycolysis.htm The chemical logic behind glycolysis] at ufp.pt
* [http://www.expasy.org/tools/pathways/boehringer_legends.html Expasy biochemical pathways poster] at [[ExPASy]]
* {{MedicalMnemonics|317|5468||}}
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