The biosynthesis of oligosaccharide-lipids. Partial purification and characterization of mannosyltransferase II.
A mannosyltransferase that catalyzes transfer from GDP-mannose to tetrasaccharide-pyrophosphoryl-lipid with the formation of the alpha-1,3-mannosyl-mannose linkage in Man alpha 1-3(Man alpha 1-6)Man beta-GlcNAc beta-GlcNAc-P-P-lipid has ben purified 660-fold from rabbit liver microsomes. The enzyme was completely separated from mannosyltransferases that synthesize alpha-1,2-mannosyl-mannose linkages, but the purified preparation still contained some activity which synthesized alpha-1,6-mannosyl linkages. The enzyme has a requirement for divalent cations and a pH optimum between 6.8 and 7.3, and the purified enzyme was very sensitive to detergent concentration with optimal activity at 0.0225% Nonidet P-40. The extent of purification of the enzyme and its resistance to inhibition by amphomycin strongly suggest that the enzyme catalyzes direct transfer from nucleotide-sugar to the oligosaccharide-lipid acceptor.
D000818:Animals; D006017:Glycolipids / Q000096:biosynthesis*; D006602:Hexosyltransferases / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008364:Mannosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D009844:Oligosaccharides / Q000378:metabolism*; D011817:Rabbits
D006017:Glycolipids; D009844:Oligosaccharides; D006602:Hexosyltransferases; D008364:Mannosyltransferases; C033143:glycolipid 3-alpha-mannosyltransferase