Purification and characterization of the Escherichia coli K1 neuB gene product N-acetylneuraminic acid synthetase

Willie F. Vann, Jose J. Tavarez, Jane Crowley, Eric Vimr, Richard P. Silver

Research output: Contribution to journalArticlepeer-review


Escherichia coil K1 produces a capsular polysaccharide of α(2-8) poly-N-acetylneuraminic acid. This polysaccharide is an essential virulence factor of these bacteria. The genes necessary for the synthesis of neuAc were localized to a plasmid containing the neuBAC genes of the K1 gene cluster. Cells harboring the neuB+ allele in an aldolase (nanA-) negative background produce neuNAc in vivo. Enzymatic synthesis Of neuNAc could be demonstrated in extracts of cells harboring an expression plasmid (pNEUB) containing the neuB gene alone. NeuNAc synthetase was purified to homogeneity from extracts of cells harboring pNEUB. The molecular weight of the purified enzyme is 40 kDa, similar to that predicted by the nucleotide Sequence of the neuB Gene. The amino terminal sequence of the purified protein matches that predicted by the nucleotide sequence of the neuB gene. NeuNAc synthetase catalyzes the formation of neuNAc as indicated by its coupling to the CMP-neuNAC synthetase reaction. The enzyme condenses manNAC and PEP with the release of phosphate. The E. coli neuNAc synthetase is specific for manNAc and PEP, unlike rat liver enzyme that utilizes N-acetylmannosamine- 6-phosphate to form neuNAc-9-PO4. This represents the first report of a purification of a sialic acid synthetase from either a eukaryotic or prokaryotic source to homogeneity. These experiments clearly demonstrate an aldolase-independent sialic acid synthetase activity in E.coli K1.

Original languageEnglish (US)
Pages (from-to)697-701
Number of pages5
Issue number5
StatePublished - Jul 1997


  • Acid
  • E.coli neuB
  • Enzyme purification/polysialic
  • Sialic acid Synthetase
  • Sialic acid metabolism

ASJC Scopus subject areas

  • General Medicine


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