Alpha-D-phosphohexomutase, alpha/beta/alpha domain II (IPR005845)

Short name: A-D-PHexomutase_a/b/a-II

Overlapping homologous superfamilies

Domain relationships



The alpha-D-phosphohexomutase superfamily is composed of four related enzymes, each of which catalyses a phosphoryl transfer on their sugar substrates: phosphoglucomutase (PGM), phosphoglucomutase/phosphomannomutase (PGM/PMM), phosphoglucosamine mutase (PNGM), and phosphoacetylglucosamine mutase (PAGM) [PMID: 10506283]. PGM (EC: converts D-glucose 1-phosphate into D-glucose 6-phosphate, and participates in both the breakdown and synthesis of glucose [PMID: 15299905]. PGM/PMM (EC:; EC: are primarily bacterial enzymes that use either glucose or mannose as substrate, participating in the biosynthesis of a variety of carbohydrates such as lipopolysaccharides and alginate [PMID: 16595672, PMID: 14725765]. Both PNGM (EC: and PAGM (EC: are involved in the biosynthesis of UDP-N-acetylglucosamine [PMID: 10913078, PMID: 11004509].

Despite differences in substrate specificity, these enzymes share a similar catalytic mechanism, converting 1-phospho-sugars to 6-phospho-sugars via a biphosphorylated 1,6-phospho-sugar. The active enzyme is phosphorylated at a conserved serine residue and binds one magnesium ion; residues around the active site serine are well conserved among family members. The reaction mechanism involves phosphoryl transfer from the phosphoserine to the substrate to create a biophosphorylated sugar, followed by a phosphoryl transfer from the substrate back to the enzyme [PMID: 15238632].

The structures of PGM and PGM/PMM have been determined, and were found to be very similar in topology. These enzymes are both composed of four domains and a large central active site cleft, where each domain contains residues essential for catalysis and/or substrate recognition. Domain I contains the catalytic phosphoserine, domain II contains a metal-binding loop to coordinate the magnesium ion, domain III contains the sugar-binding loop that recognises the two different binding orientations of the 1- and 6-phospho-sugars, and domain IV contains a phosphate-binding site required for orienting the incoming phospho-sugar substrate.

This entry represents domain II found in alpha-D-phosphohexomutase enzymes. This domain has a 3-layer alpha/beta/alpha topology.

GO terms

Biological Process

GO:0005975 carbohydrate metabolic process

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.