The alpha-D-phosphohexomutase superfamily includes several related enzymes that catalyze a reversible intramolecular phosphoryl transfer on their sugar substrates. Members of this family include the phosphoglucomutases (PGM1 and PGM2), phosphoglucosamine mutase (PNGM), phosphoacetylglucosamine mutase (PAGM), the bacterial phosphomannomutase ManB, the bacterial phosphoglucosamine mutase GlmM, and the bifunctional phosphomannomutase/phosphoglucomutase (PMM/PGM). These enzymes play important and diverse roles in carbohydrate metabolism in organisms from bacteria to humans. Each of these enzymes has four domains with a centrally located active site formed by four loops, one from each domain. All four domains are included in this alignment model.