The role of mannosylphosphorylpolyisoprenol in glycoprotein biosynthesis in Mycobacterium smegmatis

Abstract

A particulate enzyme preparation of Mycobacterium smegmatis catalyzes the transfer of labeled mannose from GDP-[14C] mannose into several endogenous acceptors. In one of these transfer reactions, the radioactivity is incorporated into an insoluble polymeric product that is present at the interphase after extraction of reaction mixture with chloroform-methanol. Solubilization of this product was achieved by digestion with proteolytic enzymes or treatment with 0.1 M NaOH indicating that the material was glycoprotein in nature. The solubilized material obtained after proteolytic digestion followed by treatment with alkali (representing 80-93% of the total interphase product) was shown to consist of a series of small molecular weight [14C] mannose containing oligosaccharides and glycopeptides by Bio-Gel column chromatography. A kinetic study of the enzymatic transfer of [14C] mannose from GDP-[14C] mannose into the glycoprotein suggested that the mannosylphosphorylpolyisoprenols are the obligatory mannosyl donor.