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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.
d -Glucose + 2 [NAD] + + 2 [ADP] + 2 [P] i 2 × Pyruvate 2 × + 2 [NADH] + 2 H + + 2 [ATP] + 2 H 2 O Glycolysis pathway overview The use of symbols in this equation makes it appear unbalanced with respect to oxygen atoms, hydrogen atoms, and charges. Atom balance is maintained by the two phosphate (P i) groups: Each exists in the form of a hydrogen phosphate anion, dissociating to contribute ...
The reaction is similar to the reaction catalysed by pyruvate kinase, which also converts pyruvate to PEP. [3] However, pyruvate kinase catalyses an irreversible reaction, and does not consume ATP. By contrast, PPDK catalyses a reversible reaction, and consumes 1 molecule of ATP for each molecule of pyruvate converted.
Many Enterobacteriaceae, including E. coli, have two isoforms of pyruvate kinase, PykA and PykF, which are 37% identical in E. coli (Uniprot: PykA, PykF).They catalyze the same reaction as in eukaryotes, namely the generation of ATP from ADP and PEP, the last step in glycolysis, a step that is irreversible under physiological conditions.
Pyruvate, the conjugate base, CH 3 COCOO −, is an intermediate in several metabolic pathways throughout the cell. Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or converted to fatty acids through a reaction with acetyl-CoA. [3]
Figure 3 shows this metabolic flow (and its regulation). Similar to pyruvate carboxylase, PEP carboxylase replenishes oxaloacetate in the citric acid cycle. At the end of glycolysis, PEP is converted to pyruvate, which is converted to acetyl-coenzyme-A , which enters the citric acid cycle by reacting with oxaloacetate to form citrate. To ...
When pyruvate kinase – the enzyme that normally catalyzes the reaction that converts PEP to pyruvate – is knocked out in mutants of Bacillus subtilis, PEPCK participates in one of the replacement anaplerotic reactions, working in the reverse direction of its normal function, converting PEP to OAA. [13] Although this reaction is possible ...
Phosphopyruvate hydratase, usually known as enolase, is a metalloenzyme (EC 4.2.1.11) that catalyses the conversion of 2-phosphoglycerate (2-PG) to phosphoenolpyruvate (PEP), the ninth and penultimate step of glycolysis. The chemical reaction is: 2-phospho-D-glycerate phosphoenolpyruvate + H 2 O