Phosphoglucomutase

Phosphoglucomutase (EC 5.4.2.2) is an enzyme that transfers a phosphoryl group on a glucose monomer from the 1′ to the 6′ position in the forward direction or the 6′ to the 1′ position in the reverse.

More specifically, it facilitates the interconversion of glucose 1-phosphate and glucose 6-phosphate.

After glycogen phosphorylase has broken off a single glucose molecule from the greater glycogen structure, the free glucose has a phosphate group on its 1-carbon. This glucose-1-phosphate isomer cannot be metabolized easily. The enzyme phosphoglucomutase phosphorylates the 6-carbon, while subsequently dephosphorylating the 1-carbon. The result is glucose-6-phosphate, which can now theoretically travel down the glycolysis or pentose phosphate pathway.

Phosphoglucomutase also acts in the opposite fashion when a large concentration of glucose-6-phosphate is present. In this case, it is the 1-carbon that is phosphorylated and the 6-carbon that is dephosphorylated. The resulting glucose-1-phosphate is then changed into UDP-glucose in a number of intermediate steps. If activated by insulin, glycogen synthase will proceed to clip the glucose from the UDP-glucose complex and on to the glycogen molecule.

Human muscle contains two phosphoglucomutases with nearly identical catalytic properties, PGM I and PGM II. One or the other of these forms is missing in some humans congenitally.

Phosphoglucomutase deficiency is an extremely rare condition that does not have a set of well-characterized physiological symptoms. This condition can be detected by an in vitro study of anaerobic glycolysis which reveals a block in the pathway toward lactic acid production after glucose 1-phosphate but before glucose 6-phosphate.

• PGM1, PGM2, PGM3, PGM5

• Mutase

• Phosphoglucomutase at the US National Library of Medicine Medical Subject Headings (MeSH)