2phosphoglycerate

2-phosphoglycerate (2-PG) is a three-carbon phosphorylated metabolite that functions as an intermediate in central carbohydrate metabolism, notably glycolysis and gluconeogenesis. It is formed from 3-phosphoglycerate by the enzyme phosphoglycerate mutase and is subsequently converted to phosphoenolpyruvate by enolase, with the release of a water molecule.

Enzymology and structure: The interconversion between 3-phosphoglycerate and 2-phosphoglycerate is catalyzed by phosphoglycerate mutase (PGAM). There are two major classes of PGAM: cofactor-dependent and cofactor-independent. The former typically relies on a phosphorylated intermediate or donor for catalysis, while the latter uses metal ions to drive the mutase reaction. In both cases, the reaction can proceed in either direction depending on cellular conditions and metabolite levels.

Pathway role: In glycolysis, 2-PG sits between 3-PG and phosphoenolpyruvate. The subsequent step, 2-PG to PEP, is catalyzed by enolase and contributes to energy capture later in the pathway through downstream reactions that generate ATP. The 3-PG ↔ 2-PG interconversion is generally near equilibrium, so flux through glycolysis versus gluconeogenesis is influenced by the overall metabolic state and enzyme regulation.

Occurrence and significance: 2-PG is present in many organisms, including bacteria, archaea, and eukaryotes. As a glycolytic intermediate, its levels reflect pathway flux and can be affected by perturbations in PGAM or enolase activity, influencing the balance between energy production and carbohydrate synthesis.