BIOSYNTHESIS OF MANNOSE-CONTAINING GLYCOPROTEINS - A POSSIBLE LIPID INTERMEDIATE

Particulate fractions from liver, oviduct, and myeloma tumor incorporated mannose-14C from GDP-mannose-14C into glycoprotein and lipid. Smooth membranes from rabbit liver were purified 8-fold with respect to incorporation of mannose-14C into endogenous lipid acceptor; the mannolipid appeared similar in many respects to the mannosyl-1-phosphoryl-polyisoprenol compound found in bacteria. Incorporation into lipid was 7 times greater than into protein when incubated in the presence of 6 × 10-3 M MnCl2, 2.5 × 10-3 M EDTA, and 0.15% Zonyl A. The role of lipid as a possible intermediate in the biosynthesis of secreted, soluble glycoproteins is discussed; a minimum of two mannosyl transferases are required. © 1969.