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Phosphoenolpyruvate

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Title: Phosphoenolpyruvate  
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Phosphoenolpyruvate

Phosphoenolpyruvic acid

Identifiers
CAS number 138-08-9 YesY
PubChem 1005
ChemSpider 980 YesY
DrugBank DB01819
ChEBI CHEBI:44897 YesY
Jmol-3D images Image 1
Properties
Molecular formula C3H5O6P
Molar mass 168.04 g mol−1
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.

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
   
  Enolase   Pyruvate kinase

Compound KEGG Pathway Database.

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

Interactive pathway map

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. 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.

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 + HCO3- → oxaloacetate

References


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