Glycolipid intermediates involved in the transfer of N-acetylglucosamine to endogenous proteins in a yeast membrane preparation.
A particulate membrane fraction from Saccharomyces cerevisiae contains transferases which catalyze the incorporation of N-acetylglucosamine from UDP-N-acetylglucosamine into a lipid fraction as well as into a protein fraction. The lipid fraction contains two alkali-stable lipids which can be separated on a silica G-60 column. The sugar moieties of these polyprenoid lipids are: N-acetylglucosamine and di-N-acetylchitobiose. The transfer of carbohydrate from isolated glycolipids to endogenous protein has been examined. After separation of protein and saccharide by hydrazinolysis and reacetylation only di-N-acetylchitobiose is found, and also when glycolipid containing only one N-acetylglucosamine is used as substrate. Maximum transfer of saccharides from glycolipids to protein is obtained at a Triton X-100 concentration of 1%. At this Triton X-100 concentration there is practically no transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to the phosphorylated lipid. Therefore, when polyprenyl diphosphate N-acetyl[3H]-glucosamine is incubated together with UDP-N-acetyl[14C]glucosamine with the membrane fraction in the presence of 1% Triton X-100, a doubly labelled di-N-acetylchitobiose linked to lipid is formed with N-acetyl[14C]glucosamine at the non-reducing end of the chain.