This family of glycosyl hydrolases contains vacuolar acid trehalase and maltose phosphorylase.Maltose phosphorylase (MP) is a dimeric enzyme that catalyses the conversion of maltose and inorganic phosphate into beta-D-glucose-1-phosphate and glucose. The central domain is the catalytic domain, which binds a phosphate ion that is proximal the the highly conserved Glu. The arrangement of the phosphate and the glutamate is thought to cause nucleophilic attack on the anomeric carbon atom [1]. The catalytic domain also forms the majority of the dimerisation interface.

1: Crystal structure of maltose phosphorylase from Lactobacillus brevis: unexpected evolutionary relationship with glucoamylases. Egloff MP, Uppenberg J, Haalck L, van Tilbeurgh H; Structure (Camb) 2001;9:689-697. PMID:11587643