Polyisoprenyl phosphate specificity of a soluble form of GlcNAc-P-pundecaprenol synthase from E. coli

J. S. Rush, P. D. Rick, C. J. Waechter

Research output: Contribution to journalArticlepeer-review


GlcNAc-P-P-Undecaprenol (GicNAc-P-P-Und), an intermediate in the biosynthesis of the enterobacterial common antigen in E. coli and some Oantigen chains in gram-negative bacteria, is formed by the transfer of GlcNAc 1P from UDP-GlcNAc to Und-P. GlcNAc-P-P-dolichol (GlcNAc-P-P-Dol) is formed by a similar reaction in mammalian cells. Since the microsomal enzyme from animal cells preferentially utilizes Dol-P which contains a saturated a-isoprene unit, the polyisoprenyl phosphate specificity of the bacterial enzyme was characterized. The E. coli enzyme unexpectedly was enriched in the 175,000g supernatant fraction (80%) compared to the paniculate fraction (20%). GlcNAcP-P-Und synthase activity was elevated in the soluble and participate fractions obtained from a strain of E. coli bearing the rfe gene, which encodes GlcNAc-PP-Und synthase, on a multi-copy plasmid, and virtually absent from both fractions in rfe null mutants. The enzyme is apparently cytosolic since it cofractionates with β-galactosidase, and not with the periplasmic enzyme marker, alkaline phosphatase. The soluble GlcNAc-P-P-Und synthase activity was dependent on the addition of exogenous polyprenyl phosphate substrates with maximal activity seen with (C55)Und-P. The E. coli enzyme was unable to utilize (C55)Dol-P which contains a saturated a-isoprene unit. In contrast to the E. co/i enzyme, GlcNAc-P-P-Dol synthase (also referred to as GPT in mammalian cells), associated with pig brain microsomes utilized (C55)Dol-P, but not Und-P, as substrate. GlcNAc-P-P-Und synthase activity bound to paniculate fractions from three strains of bacilli also exhibited a preference for fully unsaturated polyprenyl phosphate substrates. The functional significance of the use of polyisoprenols with saturated a-isoprene units in eukaryotes remains uncertain.

Original languageEnglish
Pages (from-to)A1240
JournalFASEB Journal
Issue number6
StatePublished - 1996

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics


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