BIOSYNTHESIS OF THE GLYCOSYL PHOSPHATIDYLINOSITOL MEMBRANE ANCHOR OF THE TRYPANOSOME VARIANT SURFACE GLYCOPROTEIN - ORIGIN OF THE NON-ACETYLATED GLUCOSAMINE

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  • 5 July 1989
    • journal article
    • research article
    • Vol. 264  (19) , 11168-11173
Abstract
Non-acetylated glucosamine is an unusual structural feature shared by all glycosyl phosphatidylinositol (GPI) lipids, including a variety of membrane anchors, the leishmanial lipophosphoglycan, and a mediator of insulin action. We proposed previously a pathway for biosynthesis of glycolipid A, the precursor of the GPI membrane anchor of the trypanosome variant surface glycoprotein (Masterson, W.J., Doering, T.L., Hart, G. W., and England, P. T. (1989) Cell 56, 793-800). In this paper we characterize in more detail the initial steps of GPI assembly. The first and committed step in the pathway is the transfer of GlcNAc, from UDP-GlcNac, to endogeneous phosphatidylinositol to form N-acetylglucosaminyl phosphatidylinositol (GlcNAc-PI). The GlcNAc-PI is then efficiently deacetylated to form glucosaminyl phosphatidylinositol (GlcN-PI), the substrate for subsequent reactions en route to glycolipid A.