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Phosphoenolpyruvate Information

Phosphoenolpyruvic acid (PEP), or phosphoenolpyruvate as the anion, 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 bacteria, it is also used as the source of energy for the phosphotransferase system.

Contents

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 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.

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 ā†’ GDP + phosphoenolpyruvate + CO2

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.

In addition, in Cā‚„ plants, PEP serves as an important substrate in carbon fixation. The chemical equation, as catalyzed by phosphoenolpyruvate carboxylase (PEP carboxylase), is:

PEP + HCO3- ā†’ oxaloacetate

References

  1. ^ "InterPro: IPR008209 Phosphoenolpyruvate carboxykinase, GTP-utilising". http://www.ebi.ac.uk/interpro/IEntry?ac=IPR008209. Retrieved 2007-08-17.
  2. ^ "BioCarta - Charting Pathways of Life". http://www.biocarta.com/pathfiles/chorismatePathway.asp. Retrieved 2007-08-17.
Glycolysis Metabolic Pathway
Glucose Hexokinase Glucose 6-phosphate Glucose-6-phosphate isomerase Fructose 6-phosphate phosphofructokinase-1 Fructose 1,6-bisphosphate Fructose bisphosphate aldolase
ATP ADP ATP ADP
Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Triosephosphate isomerase Glyceraldehyde 3-phosphate Glyceraldehyde-3-phosphate dehydrogenase 1,3-Bisphosphoglycerate
NAD+ + Pi NADH + H+
+ 2 2
Phosphoglycerate kinase 3-Phosphoglycerate Phosphoglycerate mutase 2-Phosphoglycerate Phosphopyruvate hydratase(Enolase) Phosphoenolpyruvate Pyruvate kinase Pyruvate
ADP ATP H2O ADP ATP
2 2 2 2

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