Restoration by phospholipids of dolichol pyrophosphate N-acetylglucosamine synthesis in delipidated rat lung microsomes.

Abstract

The effects of phospholipids on the reaction catalyzed by UDP-GlcNAc:dolichol phosphate GlcNAc-1-phosphate transferase have been studied with delipidated rat lung microsomes. Deoxycholate-solubilized enzyme was depleted of measurable phospholipid by either gel filtration on Sephadex G-100 or affinity chromatography on pentyl-agarose. The latter procedure also removed nucleotide and sugar nucleotide hydrolases. Delipidated protein fractions were devoid of GlcNAc-1-phosphate transferase activity unless supplemented with phospholipids. Maximal recovery of enzyme activity was obtained with an approximate 1:1 weight ratio of phosphatidylglycerol:phosphatidylcholine, with the observed rate being synergistic as compared to rates observed for each individual phospholipid. Variable recoveries of enzyme activity were obtained with mixtures containing other acidic phospholipids and phosphatidylcholine. Enzyme activity in the fraction eluted from pentyl-agarose could be recovered, after removal of Triton X-100, with sedimented phospholipid vesicles. Significant stabilization of enzyme activity associated with the phospholipid vesicles was obtained by the inclusion of dolichol phosphate.