fosfoglukomutazy

Fosfoglukomutazy, known in English as phosphoglucomutases (PGM), are enzymes that catalyze the reversible interconversion of glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P). This reaction links glycogen and starch metabolism with glycolysis, gluconeogenesis, and the biosynthesis of nucleotide sugars used for polysaccharide formation.

The reaction they catalyze is bidirectional and depends on the cellular concentrations of substrates and products. In glycogen metabolism, G1P is produced for UDP-glucose formation, which in turn feeds glycogen synthesis. In glycolysis and the pentose phosphate pathway, G6P serves as a key entry point for energy production and biosynthetic precursors.

Phosphoglucomutases belong to the alpha-D-phosphoglucomutase superfamily. Their catalytic cycle involves a phosphorylated serine residue in the active site and a transient sugar-phosphate intermediate within the enzyme. Most PGM enzymes require divalent cations, such as Mg2+, for activity. The mechanism is typically described as a phosphoserine covalent intermediate with rearrangement of the phosphate group on the sugar moiety.

Organisms harbor multiple PGM genes, with several isoforms in higher eukaryotes. In humans, notable isoforms include PGM1, PGM2, and PGM3, each with distinct tissue distribution or substrate preferences; PGM3 also participates in related sugar-phosphate pathways.

Deficiencies in PGM1, for example, can cause a congenital disorder of glycosylation (CDG) with a spectrum of clinical features, including liver dysfunction, growth delay, and immune abnormalities. Phosphoglucomutases are widespread and essential for proper carbohydrate metabolism across life.