Phosphoenolpyruvate

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ImageFile=Phosphoenolpyruvic acid.svg
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IUPACName=2-phosphonooxyprop-2-enoic acid
OtherNames=Phosphoenolpyruvic acid, PEP
Section1= Chembox Identifiers
CASNo=138-08-9
PubChem=1005
ChemSpiderID = 980
SMILES=C=C(C(=O)O)OP(=O)(O)O
Section2= Chembox Properties
Formula=C₃H₅O₆P
MolarMass=168.042
Appearance=
Density=
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Section3= Chembox Hazards
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Phosphoenolpyruvate (synonyms: phosphoenolpyruvic acid, PEP) is an important chemical compound in biochemistry. It has the high-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 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.

Biochemical Reaction
reaction_A_major_substrate=2-phospho-D-glycerate
reaction_A_major_substrate_

reaction_A_foward_enzyme=Enolase
reaction_A_reverse_enzyme=Enolase
reaction_A_reaction_direction_(forward/reversible/reverse)=reversible
reaction_A_minor_reverse_product(s)=
reaction_A_minor_reverse_substrate(s)=H₂O
reaction_A_minor_foward_substrate(s)=
reaction_A_minor_foward_product(s)=H₂O
reaction_A_major_product=phosphoenolpyruvate
reaction_A_major_product_

reaction_B_foward_enzyme=Pyruvate kinase
reaction_B_reverse_enzyme=Pyruvate kinase
reaction_B_reaction_direction_(foward/reversible/reverse)=reversible
reaction_B_minor_foward_substrate(s)=ADP
reaction_B_minor_foward_product(s)=ATP
reaction_B_minor_reverse_product(s)=
reaction_B_minor_reverse_substrate(s)=
reaction_B_major_product=pyruvate
reaction_B_major_product_

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: [cite web |url=http://www.ebi.ac.uk/interpro/IEntry?ac=IPR008209 |title=InterPro: IPR008209 Phosphoenolpyruvate carboxykinase, GTP-utilising |accessdate=2007-08-17 |format= |work=]

:GTP + oxaloacetate → GDP + phosphoenolpyruvate + CO₂

In plants

PEP may be used for the synthesis of chorismate through the shikimate pathway. [cite web |url=http://www.biocarta.com/pathfiles/chorismatePathway.asp |title=BioCarta - Charting Pathways of Life |accessdate=2007-08-17 |format= |work=] 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

References