Novel Catalytic Mechanism of Glycoside Hydrolysis Based on the Structure of an NAD+/Mn2+-Dependent Phospho-α-Glucosidase from Bacillus subtilis

Abstract GlvA, a 6-phospho-α-glucosidase from Bacillus subtilis , catalyzes the hydrolysis of maltose-6′-phosphate and belongs to glycoside hydrolase family GH4. GH4 enzymes are unique in their requirement for NAD(H) and a divalent metal for activity. We have determined the crystal structure of GlvA in complex with its ligands to 2.05 A resolution. Analyses of the active site architecture, in conjunction with mechanistic studies and precedent from the nucleotide diphosphate hexose dehydratases and other systems, suggest a novel mechanism of glycoside hydrolysis by GlvA that involves both the NAD(H) and the metal.