Identification of Bacillus selenitireducens MLS10 maltose phosphorylase possessing synthetic ability for branched α-d-glucosyl trisaccharides Original Research Article

We discovered an inverting maltose phosphorylase (Bsel2056) belonging to glycoside hydrolase family 65 from Bacillus selenitireducens MLS10, which possesses synthetic ability for α-d-glucosyl disaccharides and trisaccharides through the reverse phosphorolysis with β-d-glucose 1-phosphate as the donor. Bsel2056 showed the flexibility for monosaccharide acceptors with alternative C2 substituent (2-amino-2-deoxy-d-glucose, 2-deoxy-d-arabino-hexose, 2-acetamido-2-deoxy-d-glucose, d-mannose), resulting in production of 1,4-α-d-glucosyl disaccharides with strict regioselectivity. In addition, Bsel2056 synthesized two maltose derivatives possessing additional d-glucosyl residue bound to C2 position of the d-glucose residue at the reducing end, 1,4-α-d-glucopyranosyl-[1,2-α-d-glucopyranosyl]-d-glucose and 1,4-α-d-glucopyranosyl-[1,2-β-d-glucopyranosyl]-d-glucose, from 1,2-α-d-glucopyranosyl-d-glucose (kojibiose) and 1,2-β-d-glucopyranosyl-d-glucose (sophorose), respectively, as the acceptors. These results suggested that Bsel2056 possessed a binding space to accommodate the bulky C2 substituent of d-glucose.