Phosphoglucomutase

Phosphoglucomutase is an enzyme that catalyzes the reversible conversion between glucose-1-phosphate and glucose-6-phosphate. This reaction links glycogen metabolism, glycolysis, and the biosynthesis of sugar nucleotides. It is present across bacteria, archaea, and eukaryotes, and operates in the cytosol of most cells. The produced glucose-6-phosphate can enter glycolysis or the pentose phosphate pathway, while glucose-1-phosphate is a substrate for glycogen synthesis and for generating UDP-glucose used in glycosylation and polysaccharide biosynthesis.

There are two established families of phosphoglucomutase enzymes. Cofactor-dependent PGM (dPGM) enzymes rely on a divalent metal ion and form a covalent phosphoserine intermediate during turnover. Cofactor-independent PGM (iPGM) enzymes do not require a phosphoenzyme intermediate and use a different catalytic strategy, though both families achieve the same net reaction.

In humans, the PGM1 gene encodes a cytosolic enzyme that participates in glycogen metabolism and glucose utilization. In microorganisms, PGM homologs contribute to carbohydrate metabolism and cell wall biosynthesis. The enzymes can vary in size, structure, and oligomeric state between families.

Genetic mutations in PGM1 can cause a congenital disorder of glycosylation (PGM1-CDG), with symptoms reflecting impaired glycosylation and variable systemic involvement. Study of PGM enzymes informs understanding of metabolic flux between glycogen breakdown and glucose utilization and has potential relevance to metabolic diseases.