Lipid carriers in the synthesis of high-mannose glycoproteins in algae.
Particulate preparations from the chlorophyta Prototheca zopfii catalyze the incorporation of mannose and N-acetylglucosamine into glycolipids. These had been characterized as lipid monophosphate mannose, lipid pyrophosphate N,N'-diacetylchitobiose and various lipid-linked oligosaccharides containing two N-acetylglucosamine residues plus a variable number of mannose residues. The lipid moiety has the properties expected for dolichyl phosphate. The oligosacchride-linked lipids serve as precursors for the formation of a polymer sensible to pronase digestion. The oligosaccharide is linked by N-glycosidic linkage to an asparagine residue. In longer incubation periods, a polymer insensitive to pronase hydrolysis, but precipitable by copper salts such as cell wall mannans is formed. Polymer formation is inhibited by 1 mM bacitracin. The reactions leading to the formation of the mannoprotein were found associated to the rough endoplasmic reticulum. The synthesis of mannans was found to occur in the Golgi vesicles.
D000117:Acetylglucosamine / Q000378:metabolism; D001414:Bacitracin / Q000494:pharmacology; D000460:Chlorophyta / Q000378:metabolism*; D006017:Glycolipids / Q000378:metabolism*; D006023:Glycoproteins / Q000096:biosynthesis*; D007425:Intracellular Membranes; D008358:Mannose / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism
D006017:Glycolipids; D006023:Glycoproteins; D009844:Oligosaccharides; D001414:Bacitracin; D008358:Mannose; D000117:Acetylglucosamine