A mannosyl-carrier lipid of bovine adrenal meddulla and rat parotid.
1. The transfer of mannose from GDP-(U-14-C)mannose into endogenous acceptors of bovine adrenal medullla and rat parotid was studied. The rapidly labelled product, a glycolipid, was partially purified and characterized. 2. It was stable to mild alkaline hydrolysis but yielded (14-C)mannose on mild acid hydrolysis. It co-chromatographed with mannosyl phosphoryl dolichol in four t.l.c. systems and on DEAE-cellulose acetate. Addition of dolichol phosphate or a dolichol phosphate-enriched fraction prepared from pig liver stimulated mannolipid synthesis. 3. The formation of mammolipid appeared reversible, since addition of GDP to a system synthesizing the mannolipid caused a rapid loss of label from the mannolipid. UDP-N-acetylglucosamine did not inhibit mannolipid synthesis except at high concentrations (2 mM), even though in the absence of GDP-mannose, N-acetylglucosamine was incorporated into a lipid having the properties of a glycosylated polyprenyl phosphate. 4. Mannose from GDP-mannose was also incorporated into two other acceptors, (2y being insoluble in chloroform-methanol (2:1, v/v) but soluble in choloroform-methanol-water (10:10:3, by vol.) and (ii) protein. These are formed much more slowly than the mannolipid. 5. Exogenous mannolipid served as a mannose donor for acceptors (i) and (ii), and it is suggested that transfer of mannose from GDP-mannose to mannosylated protein occurs via two intermediates, the mannolipid and acceptor (i).
D000117:Acetylglucosamine; D000313:Adrenal Medulla / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes; D002417:Cattle; D002458:Cell Fractionation; D002848:Chromatography, DEAE-Cellulose; D002855:Chromatography, Thin Layer; D004286:Dolichols; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D006868:Hydrolysis; D008024:Ligands; D050356:Lipid Metabolism; D008358:Mannose / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D010306:Parotid Gland / Q000378:metabolism; D051381:Rats
D002250:Carbon Radioisotopes; D004286:Dolichols; D008024:Ligands; D006155:Guanosine Diphosphate Mannose; D008358:Mannose; D000117:Acetylglucosamine