M. Petersen et al., The siaA gene involved in capsule polysaccharide biosynthesis of Neisseriameningitidis B codes for N-acylglucosamine-6-phosphate 2-epimerase activity, FEMS MICROB, 184(2), 2000, pp. 161-164
The capsule polysaccharide of Neisseria meningitidis serogroup B is compose
d of a homopolymer of alpha-2 --> 8 linked N-acetyl-neuraminic acid (sialic
acid). The enzymes required for sialic acid biosynthesis and polymerizatio
n are encoded in region A of the capsule gene complex. We here describe the
enzymatic activity of the siaA gene product as determined by biochemical a
nalysis. siaA was overexpressed in Escherichia coli and the SiaA protein wa
s purified to homogeneity. Enzymatic assays revealed that SiaA did not acce
pt N-acetyl-glucosamine as substrate, but only N-acetyl-glucosamine-6-phosp
hate (EC 5.1.3.9). SiaA catalyzes the isomerization of N-acetyl-glucosamine
-6-phosphate to form N-acetyl-mannosamine-6-phosphate. This reaction repres
ents the first step in capsule biosynthesis of N. meningitidis B. (C) 2000
Federation of European Microbiological Societies. Published by Elsevier Sci
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