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Phosphoenolpyruvic acid
Chemical compound From Wikipedia, the free encyclopedia
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Phosphoenolpyruvate (2-phosphoenolpyruvate, PEP) is the carboxylic acid derived from the enol of pyruvate and phosphate. It exists as an anion. PEP is an important intermediate in biochemistry. It has the highest-energy phosphate bond found (−61.9 kJ/mol) in 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; in bacteria, it is also used as the source of energy for the phosphotransferase system.[1][2]
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In glycolysis
PEP is formed by the action of the enzyme enolase on 2-phosphoglyceric acid. Metabolism of PEP to pyruvic acid by pyruvate kinase (PK) generates 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 | ||||||
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.
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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:[3]
- GTP + oxaloacetate → GDP + phosphoenolpyruvate + CO2
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles.[§ 1]
Glycolysis and Gluconeogenesis edit
- The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534".
In plants
PEP may be used for the synthesis of chorismate through the shikimate pathway.[4] Chorismate may then be metabolized into the aromatic amino acids (phenylalanine, tryptophan and tyrosine) and other aromatic compounds. The first step is when Phosphoenolpyruvate and erythrose-4-phosphate react to form 3-deoxy-D-arabinoheptulosonate-7-phosphate (DAHP), in a reaction catalyzed by the enzyme DAHP synthase.
Biosynthesis of DAHP from phosphoenolpyruvate and erythrose-4-phosphate
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 + HCO−3 → oxaloacetate
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References
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