Torossian K, Maclachlan G
Biochim Biophys Acta. 1987 Sep 11;925(3):305-13. doi: 10.1016/0304-4165(87)90196-6.
Pea membranes supplied with GDP-[14C]mannose, UDP-N-[14C]acetylglucosamine or UDP-[14C]glucose catalyze the transfer of 14C-labeled sugars or sugar phosphates to endogenous lipid acceptors as well as to exogenously added dolichyl phosphates. Fully unsaturated polyprenyl phosphates were not used as effective acceptors by this system. Mannosyl-P-dolichol was formed most rapidly in the presence of long-chained dolichyl-P while mannosyl-PP-, glucosyl-PP- and GlcNAc-PP-dolichol were preferentially formed from relatively short-chained dolichyl phosphate acceptors. Glucosyl-PP- and mannosyl-PP-dolichol accumulated in the preparation without further metabolism, but GlcNAc-PP-dolichol was lengthened by addition of a second GlcNAc plus several [14C]mannose units to form an oligosaccharide fraction susceptible to the action of endoglycosidase H. This lipid-linked oligosaccharide could then be glycosylated in the presence of UDP-[14C]glucose to form a longer oligosaccharide. It is concluded that levels of endogenous dolichyl phosphates in pea membranes are rate-limiting for several of the key glycosyltransferases required for oligosaccharide assembly.
供给GDP-[14C]甘露糖、UDP-N-[14C]乙酰葡糖胺或UDP-[14C]葡萄糖的豌豆膜，可催化14C标记的糖或糖磷酸酯向内源脂质受体以及外源添加的多萜醇磷酸酯的转移。完全不饱和的聚异戊二烯磷酸酯不是该系统有效的受体。在长链多萜醇磷酸酯存在的情况下，甘露糖基-P-多萜醇形成得最快，而甘露糖基-PP-、葡糖基-PP-和GlcNAc-PP-多萜醇则优先由相对短链的多萜醇磷酸酯受体形成。葡糖基-PP-和甘露糖基-PP-多萜醇在制剂中积累而没有进一步代谢，但通过添加第二个GlcNAc和几个[14C]甘露糖单位，GlcNAc-PP-多萜醇会延长，形成对内切糖苷酶H作用敏感的寡糖部分。然后这种脂质连接的寡糖可以在UDP-[14C]葡萄糖存在的情况下进行糖基化，形成更长的寡糖。可以得出结论，豌豆膜中内源性多萜醇磷酸酯的水平对寡糖组装所需的几种关键糖基转移酶来说是限速的。
