Trimble R B, Byrd J C, Maley F
J Biol Chem. 1980 Dec 25;255(24):11892-5.
Glc3Man9GlcNAc2-P-P-dolichol and Man9GlcNAc2-P-P-dolichol isolated from Saccharomyces cerevisiae are substrates for the N-glycosylation of endogenous proteins in Triton X-100-solubilized yeast microsomes. The solubilized oligosaccharide transferase requires Mn2+ for activity; neither Mg2+ nor Ca2+ is an effective substitute. The pH optimum of the transfer reaction is between 6.5 and 7.5. Unlike animal systems, which utilize glucosylated oligosaccharide-lipid to a much greater extent than the unglucosylated species as a donor in the transferase rection, yeast extracts transfer more than 70% of Glc3Man9GlcNAc2 and Man9GlcNAc2 from their respective oligosaccharide-lipids to proteins. However, the rate of N-glycosylation in vitro is approximately 25-fold faster with Glc3Man9GlcNAc2-P-P-dolichol than with Man9GlcNAc2-P-P-dolichol. The apparent Km value for the glucosylated species is 75 nM, while that for the unglucosylated glycolipid is 55 nM.
从酿酒酵母中分离出的Glc3Man9GlcNAc2-P-P-多萜醇和Man9GlcNAc2-P-P-多萜醇是Triton X-100增溶的酵母微粒体中内源性蛋白质N-糖基化的底物。增溶的寡糖转移酶需要Mn2+来发挥活性；Mg2+和Ca2+都不是有效的替代物。转移反应的最适pH在6.5至7.5之间。与动物系统不同，在转移酶反应中，动物系统比未糖基化的物种更多地利用糖基化的寡糖-脂质作为供体，酵母提取物将其各自寡糖-脂质中70%以上的Glc3Man9GlcNAc2和Man9GlcNAc2转移到蛋白质上。然而，体外N-糖基化的速率在使用Glc3Man9GlcNAc2-P-P-多萜醇时比使用Man9GlcNAc2-P-P-多萜醇时快约25倍。糖基化物种的表观Km值为75 nM，而未糖基化糖脂的表观Km值为55 nM。
