Phosphoglycerate kinase (PGK; EC 2.7.2.3) is a conserved cytosolic enzyme of central carbon metabolism that catalyzes the reversible, Mg2+-dependent transfer of a phosphoryl group between 1,3-bisphosphoglycerate and ADP, yielding 3-phosphoglycerate and ATP. It is a two-domain hinge-bending enzyme in which the N-terminal domain binds the phosphoglycerate substrate and the C-terminal domain binds the adenine nucleotide; catalysis requires large domain closure to bring the two substrates into proximity. In the glycolytic direction the enzyme performs substrate-level phosphorylation to generate ATP, and in the gluconeogenic direction it runs in reverse to regenerate 1,3-bisphosphoglycerate. In Pseudomonas putida KT2440, where the classical Embden-Meyerhof-Parnas pathway is incomplete in the forward glycolytic direction (the organism lacks 6-phosphofructokinase) and glucose catabolism proceeds mainly via periplasmic oxidation and the Entner-Doudoroff pathway, Pgk operates in the lower segment of central carbon metabolism, contributing to gluconeogenesis and to glycolytic ATP generation from triose phosphates.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004618 phosphoglycerate kinase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Core molecular function. The enzyme is a member of the phosphoglycerate kinase family (Pfam PF00162; IPR001576) carrying EC 2.7.2.3 and the RHEA:14801 reaction, mapped via UniRule and InterPro2GO. This is the defining catalytic activity of the protein. |
| GO:0005524 ATP binding | IEA GO_REF:0000118 | ACCEPT | Summary: PGK binds and produces/consumes ATP as part of its catalytic cycle; the C-terminal domain forms the adenine-nucleotide binding site. ATP binding is a well-supported supporting molecular function for this enzyme. |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: PGK is a soluble cytosolic enzyme of central carbon metabolism, consistent with the UniProt subcellular location prediction. The more specific term cytosol (GO:0005829) is also annotated and is preferable. |
| GO:0005829 cytosol | IEA GO_REF:0000118 | ACCEPT | Summary: Appropriate, more specific cytosolic localization for this soluble glycolytic/gluconeogenic enzyme. Consistent with pathway placement in the central carbon network; no experimental localization assay for the P. putida ortholog, but the inference is sound for a PGK-family enzyme. |
| GO:0006094 gluconeogenesis | IEA GO_REF:0000118 | ACCEPT | Summary: PGK catalyzes a reversible reaction shared by glycolysis and gluconeogenesis. In P. putida KT2440, where forward EMP glycolysis is incomplete (no Pfk), the gluconeogenic direction is biologically important, making this an accurate process annotation. |
| GO:0006096 glycolytic process | IEA GO_REF:0000120 | ACCEPT | Summary: PGK performs the 1,3-bisphosphoglycerate to 3-phosphoglycerate step of glycolysis (UniPathway UPA00109), generating ATP by substrate-level phosphorylation. Standard and correct process annotation for this enzyme. |
| GO:0043531 ADP binding | IEA GO_REF:0000118 | ACCEPT | Summary: ADP is a substrate/product of the PGK reaction and binds in the C-terminal nucleotide-binding domain. Well-supported supporting molecular function consistent with the catalyzed reaction. |
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