Phosphoenolpyruvic acid, PEP
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Phosphoenolpyruvic acid (PEP), or phosphoenolpyruvate as the anion, 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; in bacteria, it is also used as the source of energy for the phosphotransferase system.
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.
Compound C00631 at KEGG Pathway Database. Enzyme 220.127.116.11 at KEGG Pathway Database. Compound C00074 at KEGG Pathway Database. Enzyme 18.104.22.168 at KEGG Pathway Database. Compound C00022 at KEGG Pathway Database.
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:
- GTP + oxaloacetate → GDP + phosphoenolpyruvate + CO2
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles. [§ 1]
- The interactive pathway map can be edited at WikiPathways: "GlycolysisGluconeogenesis_WP534".
PEP may be used for the synthesis of chorismate through the shikimate pathway. 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.
- PEP + HCO3− → oxaloacetate
- "InterPro: IPR008209 Phosphoenolpyruvate carboxykinase, GTP-utilising". Retrieved 2007-08-17.
- "BioCarta - Charting Pathways of Life". Retrieved 2007-08-17.
|Glycolysis Metabolic Pathway|