Heteroglycan synthesis in Cryptococcus laurentii.

An enzyme preparation from Cryptococcus laurentii catalyzes the transfer of glycosyl units from sugar nucleotides to exogenous acceptor resulting in the stepwise synthesis of a heteroglycan with the following structure: Z-O-a-n-mannosyl6-O-oc-D-mannosyl-3-~-~-D-mannosyl-(2 -0 -0 -D -xylosyl-) D-mannose. The same enzyme preparation transfers D-[‘T]mannosyl from GDP [WJmannose to an endogenous glycoprotein acceptor. Analysis of the endogenous product after mild acid hydrolysis revealed the presence of Man-2mannose, Man-3-mannose, and Man-6-mannose. The enzymes synthesizing the specific mannosyl linkages in the pentasaccharide have been shown to be distinct mannosyltransferases (SCHUTZBACH, J. S., AND ANKEL, H. (1971) J. Biol. Chem. 246, 2187-2194). The /3-xylosyl linkage in the pentasaccharide is made by an enzyme that also transfers xylose from UDP-xylose to the same endogenous acceptor