Arabinose 5-phosphate analogues as mechanistic probes for Neisseria meningitidis 3-deoxy-d-manno-octulosonate 8-phosphate synthase

3-Deoxy-d-manno-octulosonate 8-phosphate (KDO8P) synthase catalyses the condensation reaction between phosphoenolpyruvate and d-arabinose 5-phosphate (d-A5P) in a key step in lipopolysaccharide biosynthesis in Gram-negative bacteria. The KDO8P synthase from Neisseria meningitidis was cloned into Escherichia coli, overexpressed and purified. A variety of d-A5P stereoisomers were tested as substrates, of these only d-A5P and l-X5P were substrates. The Asn59Ala mutant of N. meningitidis KDO8P synthase was constructed and this mutant retained less than 1% of the wild-type activity. These results are consistent with a catalytic mechanism for this enzyme in which the C2 and C3 hydroxyl groups of d-A5P and Asn59 are critical.

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