fosfoglukomutasen

Fosfoglukomutasen, commonly known in English as phosphoglucomutase (PGM), is an enzyme that catalyzes the reversible interconversion of glucose-1-phosphate and glucose-6-phosphate. This reaction connects the metabolism of stored glucose in glycogen and starch with glycolysis and pathways derived from glucose-6-phosphate. The enzyme acts on glucose phosphates in the cytosol of most cells and is essential for efficient flux through carbohydrate metabolism.

Phosphoglucomutases operate via a ping-pong mechanism that uses a phosphorylated serine residue in the active site. In the first half-reaction, a phosphate is transferred from glucose-1-phosphate to the enzyme, forming a phosphoserine intermediate. In the second half, the phosphate is transferred from the enzyme to the glucose moiety at the 6-position, yielding glucose-6-phosphate and regenerating the active enzyme. The reaction requires divalent cations, typically Mg2+.

Biological role of fosfoglukomutasen includes providing glucose-6-phosphate for glycolysis or for conversion to UDP-glucose, which is used in glycogen and glycoprotein/glycolipid biosynthesis. It thus links glucose polymer mobilization with central carbon metabolism. In humans, the PGM1 gene encodes a cytosolic phosphoglucomutase, while other family members such as PGM2 and PGM3 have related activities with distinct tissue distributions.

Clinical relevance is seen with mutations in PGM1 and related genes, which can cause metabolic disorders including congenital disorders of glycosylation and dysglycemia with variable phenotypes. Symptoms may involve growth, immune function, or energy homeostasis, reflecting the enzyme’s role in carbohydrate metabolism and glycosylation pathways.

Structure and regulation: PGM enzymes are soluble cytosolic proteins; many bacteria have dimeric forms. Activity is magnesium-dependent and can be influenced by cellular energy status and substrate availability.