Activation of GlcNAc-P-P-Dolichol Synthesis by Mannosylphosphoryldolichol Is Stereospecific and Requires a Saturated α-Isoprene Unit

Edward L. Kean, Jeffrey S. Rush, Charles J. Waechter

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

Exogenous mannosylphosphoryldolichol (Man-P-Dol) has previously been shown to stimulate UDP-GlcNAc:dolichyl phosphate N-acetylglucosamine 1-phosphate transferase (GPT1), the enzyme catalyzing the biosynthesis of N-acetylglucosaminylpyrophosphoryldolichol (GlcNAc-P-P-Dol). To define the structural specificity of the mannolipid-mediated activation of GPT1, the ability of a variety of mannosylphosphorylisoprenols to stimulate GlcNAc-lipid biosynthesis in microsomal preparations from retinas of the embryonic chick has been tested. For these comparisons several Man-P-isoprenols were synthesized enzymatically and chemically. The catalytic efficiency of activation expressed as the Vmax/Ka. ratio was substantially higher for Man-P-Dol95 than for mannosylphosphorylpolyprenol95 (Man-P-Poly95), demonstrating that the saturated α-isoprene unit of the dolichyl moiety influences the mannolipid-enzyme interaction. The degree of activation increased with chain length and hydrophobicity of the dolichyl moiety when Man-P-dolichols containing 2, 11, and 19 isoprene units were evaluated. A strict stereospecificity was exhibited as β-Man-P-Dol95 provided a 100-fold greater stimulation than the corresponding α-stereoisomer. The recognition of the saturated α-isoprene unit, the influence of chain length, and the strict stereospecificity of the interaction between β-Man-P-Dol and GPT1 extend the description of the mannolipid-enzyme interaction and provide strong new evidence that Man-P-Dol levels can influence the rate of GlcNAc-P-P-Dol synthesis.

Original languageEnglish
Pages (from-to)10508-10512
Number of pages5
JournalBiochemistry
Volume33
Issue number34
DOIs
StatePublished - Aug 1 1994

ASJC Scopus subject areas

  • Biochemistry

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