Characterization of β-1,2-mannosyltransferase in Candida guilliermondii and its utilization in the synthesis of novel oligosaccharides

A particulate insoluble enzyme fraction containing mannosyltransferases from Candida guilliermondii IFO 10279 strain cells was obtained as the residue after extracting a 105,000 x g pellet of cell homogenate with 1% Triton X-100. Incubation of this fraction with a mannopentaose, Manα1→3(Manα1→6)Manα1→2Manα1→2Man, in the presence of GDP-mannose and Mn²⁺ ion at pH 6.0 gave a third type of β-1,2 linkage-containing mannohexaose, Man β1→2Manα1→3(Manα1→6)Manα1→2Man-α1→2Man, the structure of which was identified by means of a sequential NMR assignment. The results of a substrate specificity study indicated that the β-1,2- mannosyltransferase requires a mannobiosyl unit, Manα1→3Manα1→, at the nonreducing terminal site. We synthesized novel oligosaccharides using substrates possessing a nonreducing terminal α-1,3-linked mannose unit prepared from various yeast mannans. Further incubation of the enzymatically synthesized oligosaccharide with the enzyme fraction gave the following structure, Manβ1→2Manβ1→2Manα1→3(Manα1→6)Manα1→2Manα1→2Man, which has been found to correspond to antigenic factor 9. Incubation of Candida albicans serotype B mannan with the enzyme fraction gave significantly transformed mannan, which contains the third type of β-1,2-linked mannose units.