Phosphoenolpyruvate
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| Phosphoenolpyruvate | |
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| IUPAC name | 2-phosphonooxyprop-2-enoic acid |
| Other names | Phosphoenolpyruvic acid, PEP |
| Identifiers | |
| CAS number | [138-08-9] |
| PubChem | |
| SMILES | C=C(C(=O)O)OP(=O)(O)O |
| Properties | |
| Molecular formula | C3H5O6P |
| Molar mass | 168.042 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Phosphoenolpyruvate (synonyms: phosphoenolpyruvic acid, PEP) is an important chemical compound in biochemistry. It has the highest energy phosphate bond found (-61.9 KJ/mol) in living organisms, and is involved in glycolysis and gluconeogenesis. In plants, it is also involved in the biosynthesis of various aromatic compounds, and in carbon fixation.
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[edit] In glycolysis
PEP is formed by the action of the enzyme enolase on 2-phosphoglycerate. Metabolism of PEP to pyruvate by pyruvate kinase (PK) generates 1 molecule of adenosine triphosphate (ATP) via substrate-level phosphorylation. ATP is one of the major currencies of chemical energy within cells.
| 2-phospho-D-glycerate | Enolase | phosphoenolpyruvate | Pyruvate kinase | pyruvate | ||
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| H2O | ADP | ATP | ||||
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| H2O | ||||||
| Enolase | Pyruvate kinase | |||||
Compound C00631 at KEGG Pathway Database. Enzyme 4.2.1.11 at KEGG Pathway Database. Compound C00074 at KEGG Pathway Database. Enzyme 2.7.1.40 at KEGG Pathway Database. Compound C00022 at KEGG Pathway Database.
[edit] In gluconeogenesis
PEP is formed from the decarboxylation of oxaloacetate and hydrolysis of one guanosine triphosphate molecule. This reaction is catalyzed by the enzyme phosphoenolpyruvate carboxykinase (PEPCK). This reaction is a rate-limiting step in gluconeogenesis:[1]
- GTP + oxaloacetate → GDP + phosphoenolpyruvate + CO2
[edit] In plants
PEP may be used for the synthesis of chorismate through the shikimate pathway.[2] Chorismate may then be metabolized into the aromatic amino acids (phenylalanine, tryptophan and tyrosine) and other aromatic compounds.
In addition, in C₄ plants, PEP serves as an important substrate in carbon fixation. The chemical equation, as catalyzed by phosphoenolpyruvate carboxylase (PEP carboxylase), is:
- PEP + CO2 → oxaloacetate
[edit] References
- ^ InterPro: IPR008209 Phosphoenolpyruvate carboxykinase, GTP-utilising. Retrieved on 2007-08-17.
- ^ BioCarta - Charting Pathways of Life. Retrieved on 2007-08-17.
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