Separation and characterization of two alpha 1,2-mannosyltransferase activities from Saccharomyces cerevisiae.
Two GDP-mannose-dependent mannosyltransferase activities (designated M1MT-I and M2MT-I) from Triton X-100 extracts of Saccharomyces cerevisiae mnn1 microsomes were separated by concanavalin A lectin chromatography and partially purified. The two transferases were distinguished by differences in concanavalin A affinity and in carbohydrate acceptor specificity. Analyses of the reaction products indicate that both enzymes are alpha 1,2-mannosyltransferases. M1MT-I utilizes mannose or methyl-alpha-mannoside as acceptor while M2MT-I catalyzes the transfer of mannose from GDP-mannose to unsubstituted nonreducing alpha 1,6-linked mannose residues in the acceptor molecule. M2MT-I activity correlates with the presence of a single alpha 1,2-linked mannose residue at the nonreducing terminus of mnn2mnn9 and mnn2mnn10 outer chain oligosaccharides, and the enzyme may be involved in regulating outer chain elongation.
Lewis
M S
MS
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Ballou
C E
CE
D002240:Carbohydrate Sequence; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D006153:Guanosine Diphosphate / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D008364:Mannosyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity
D029701:Saccharomyces cerevisiae Proteins; D006153:Guanosine Diphosphate; C068701:KRE2 protein, S cerevisiae; D008364:Mannosyltransferases; C068702:mannose(2)-mannosyltransferase-I; D008358:Mannose