Chemistry:Phosphoenolpyruvic acid

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Short description: Chemical compound
Phosphoenolpyruvic acid
Phosphoenolpyruvic acid.svg
Phosphoenolpyruvic-acid-from-xtal-3D-bs-17.png
Names
Preferred IUPAC name
2-(Phosphonooxy)prop-2-enoic acid
Other names
Phosphoenolpyruvic acid, PEP
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
DrugBank
KEGG
UNII
Properties
C3H5O6P
Molar mass 168.042
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Phosphoenolpyruvate (2-phosphoenolpyruvate, PEP) is the carboxylic acid derived from the enol of pyruvate and phosphate. It exists as an anion. PEP is an important intermediate in biochemistry. It has the highest-energy phosphate bond found (−61.9 kJ/mol) in 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.[1][2]

In glycolysis

PEP is formed by the action of the enzyme enolase on 2-phosphoglyceric acid. Metabolism of PEP to pyruvic acid by pyruvate kinase (PK) generates 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
image:2-phospho-D-glycerate wpmp.png   image:phosphoenolpyruvate wpmp.png   image:pyruvate wpmp.png
H2O ADP ATP
75px Biochem reaction arrow forward YYNN horiz med.svg
H2O
   

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:[3]

GTP + oxaloacetate → GDP + phosphoenolpyruvate + CO2

Interactive pathway map

In plants

PEP may be used for the synthesis of chorismate through the shikimate pathway.[4] 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.

Biosynthesis of DAHP from phosphoenolpyruvate and erythrose-4-phosphate

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 + HCO
3
→ oxaloacetate

References

  1. Berg, Jeremy M.; Tymoczko, Stryer (2002). Biochemistry (5th ed.). New York: W.H. Freeman and Company. ISBN 0-7167-3051-0. https://archive.org/details/biochemistrychap00jere. 
  2. Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN:1-57259-153-6.
  3. "InterPro: IPR008209 Phosphoenolpyruvate carboxykinase, GTP-utilising". http://www.ebi.ac.uk/interpro/IEntry?ac=IPR008209. 
  4. "BioCarta - Charting Pathways of Life". http://www.biocarta.com/pathfiles/chorismatePathway.asp.