beta-D-Mannosidase from Helix pomatia

beta-D-Mannosidase (beta-D-mannoside mannohydrolase EC 3.2.1.25) was purified 160-fold from crude gut-solution of Helix pomatia by three chromatographic steps and then gave a single protein band (mol. wt. 94,000) on SDS-gel electrophoresis, and three protein bands (of almost identical isoelectric points) on thin-layer isoelectric focusing. Each of these protein bands had enzyme activity. The specific activity of the purified enzyme on p-nitrophenyl beta-D-mannopyranoside was 1694 nkat/mg at 40 degrees and it was devoid of alpha-D-mannosidase, beta-D-galactosidase, 2-acetamido-2-deoxy-D-glucosidase, (1 leads to 4)-beta-D-mannanase, and (1 leads to 4)-beta-D-glucanase activities, almost devoid of alpha-D-galactosidase activity, and contaminated with less than 0.02% of beta-D-glucosidase activity. The purified enzyme had the same Km for borohydride-reduced beta-D-manno-oligosaccharides of d.p. 3-5 (12.5mM). The initial rate of hydrolysis of (1 leads to 4)-linked beta-D-manno-oligosaccharides of d.p. 2-5 and of reduced beta-D-manno-oligosaccharides of d.p. 3-5 was the same, and o-nitrophenyl, methylumbelliferyl, and naphthyl beta-D-mannopyranosides were readily hydrolysed. beta-D-Mannobiose was hydrolysed at a rate approximately 25 times that of 6(1)-alpha-D-galactosyl-beta-D-mannobiose and 6(3)-alpha-D-galactosyl-beta-D-mannotetraose, and at approximately 90 times the rate for beta-D-mannobi-itol.