Partial purification and characterization of nitrophenyl maltosaccharide-hydrolyzing enzymes from Lactobacillus sp. no. 26X

Two nitrophenyl maltosaccharide-hydrolyzing enzymes were partially purified from Lactobacillus sp. no. 26X. One of the enzymes, designated nitrophenyl α-maltosidase, being a homotetramer with Mr ca. 163,000, preferentially acted on p-nitrophenyl α-maltoside. The hydrolysis rates decreased with increasing length of the nitrophenyl maltosaccharides. Maltose, maltotriose, maltotetraose, and p-nitrophenyl α-d-glucopyranoside were scarcely attacked. The enzyme mainly hydrolyzed the bond between the nitrophenyl group and the sugar moiety, and o- and p-nitrophenylated substrates were hydrolyzed equally well. The second enzyme, designated nitrophenyl α-d-glucosidase, was presumably a homodimer with Mr ca. 51,000, and was specific for p-nitrophenyl α-d-glucopyranoside. The usefulness of the nitrophenyl α-maltosidase for coupled enzymic assays for the decycling maltodextrinase and alpha-amylases with nitrophenyl maltosaccharides as the substrates is discussed.