Phosphoenolpyruvate

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Phosphoenolpyruvate (synonyms: Phosphoenolpyruvic acid, PEP) is an important chemical compound in biochemistry. It has a high energy phosphate bond, and is involved in glycolysis and gluconeogenesis. In plants, it is also involved in the biosynthesis of various aromatic compounds, and in carbon fixation.

Contents 1 In glycolysis 2 In gluconeogenesis 3 In plants 4 References 5 External links

[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
		H2O		ADP	ATP
		H2O		ADP	ATP
	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.

Additionally, 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

1. ^ [1]
2. ^ [2]

[edit] External links

• Links to external chemical sources