Biochemical and Biophysical Research Communications, 245(1):43-49, 1998. cited By 14Paper doi abstract bibtex
The 160 kDa α-mannosidase (E.C. 220.127.116.11) isolated from culture filtrate of Trichoderma reesei has wide aglycon specificity but cleaves the α1→2 and α1→3 mannosidic bonds with higher rate than α1→6 bond and slowly hydrolyses yeast mannan and 1,6-α-mannan. The specific activity of the enzyme and rate constant in the reaction with p-nitrophenyl-α-D-mannopyranoside were 0.15 U/mg and 1.62 x 10-4 μM/min/μg, respectively, at optimal pH 6.5. We have found that in vitro enzyme is able to cleave off 30% of total α-mannopyranosyl residues from N- and O-linked glycans of secreted glycoproteins. The activity of the α-mannosidase toward glycoproteins in vivo was studied comparing the structures of O- and N-linked glycans of glycoproteins isolated from the cultures growing with and without 1-deoxymannojirimycin, an inhibitor of α-mannosidases. Difference in structures of these glycans may be explained by postsecretory deglycosylation catalysed by the α-mannosidase.