A novel enzyme, maltose 1-epimerase (MER), that catalyzes the interconversion of α and β anomers of maltose was found in a cell-free extract of Lactobacillus brevis IFO 3345, and MER was purified to homogeneity from the crude extract. The M r of the enzyme was estimated to be 43,000 and 45,000 by HPLC gel filtration and SDS-PAGE, respectively. It showed optimum activity at pH 6.5–7.0. This novel enzyme catalyzed the conversion of β-maltose more effectively than disaccharides such as α-lactose and β-cellobiose, whereas the relative velocities for β- and α-d-glucose were about one forth of that for β-maltose.
