Hydrolysis of Man9GlcNAc2 and Man8GlcNAc2 oligosaccharides by a purified α-mannosidase from Candida albicans

A soluble α-mannosidase from Candida albicans was purified to homogeneity by sequential size exclusion, ion exchange, and affinity chromatographies in columns of Sepharose CL6B, DEAE Bio-Gel A, and Concanavalin A Sepharose 4B, respectively. Analytical electrophoresis of the purified preparation in 10% SDS-polyacrylamide gels stained with Coomassie blue revealed a single polypeptide of 43 kDa that was responsible for enzyme activity. The purified enzyme primarily trimmed Man 9 -GlcNAc 2 to produce Man 8 GlcNAc 2 isomer B and mannose as a function of time of incubation up to 12 h at 37°C. Prolonged incubation with the enzyme resulted in the accumulation after 24 h of other oligosaccharides corresponding to Man 7 GlcNAc 2 and probably Man 6 GlcNAc 2 . These two products were also observed when Man 8 GlcNAc 2 isomer B instead of Man 9 -GlcNAc 2 was used as substrate. Other oligosaccharides, such as Man 6 GlcNAc 2 -Asn, Man 5 GlcNAc 2 -Asn, and the α1,3- and α1,6-linked mannobiosides, were not hydrolyzed at all. These properties are consistent with an α1,2-mannosidase that may represent a new member of the glycosylhydrolase family 47.