Transglycosylating and hydrolytic activities of the beta-mannosidase from Trichoderma reesei

A purified beta-mannosidase (EC 3.2.1.25) from the fungus Trichoderma reesei has been identified as a member of glycoside hydrolase family 2 through mass spectrometry analysis of tryptic peptides. In addition to hydrolysis, the enzyme catalyzes substrate transglycosylation with p-nitrophenyl beta-mannopyranoside. Structures of the major and minor products of this reaction were identified by NMR analysis as p-nitrophenyl mannobiosides and p-nitrophenyl mannotriosides containing beta-(1 -> 4) and beta-(1 -> 3) linkages. The rate of donor substrate hydrolysis increased in presence of acetonitrile and dimethylformamide, while transglycosylation was weakly suppressed by these organic solvents. Differential ultraviolet spectra of the protein indicate that a rearrangement of the hydrophobic environment of the active site following the addition of the organic solvents may be responsible for this hydrolytic activation. (C) 2009 Elsevier Masson SAS. All rights reserved.