Characterization of CMP-N-acetylneuraminic acid synthetase of group B streptococci.
The capsular polysaccharide is a critical virulence factor for group B streptococci associated with human infections, yet little is known about capsule biosynthesis. We detected CMP-Neu5Ac synthetase, the enzyme which activates N-acetylneuraminic acid (Neu5Ac, or sialic acid) for transfer to the nascent capsular polysaccharide, in multiple group B streptococcus serotypes, all of which elaborate capsules containing Neu5Ac. CMP-Neu5Ac synthetase isolated from a high-producing type Ib strain was purified 87-fold. The enzyme had apparent Km values of 7.6 for Neu5Ac and 1.4 for CTP and a pH optimum of 8.3 to 9.4, required magnesium, and was stimulated by dithiothreitol. This is the first characterization of an enzyme involved in group B streptococcus capsular polysaccharide biosynthesis.
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115.
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Wessels
D003570:Cytidine Triphosphate / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D019158:N-Acetylneuraminic Acid; D000216:N-Acylneuraminate Cytidylyltransferase / Q000302:isolation & purification / Q000378:metabolism*; D009345:Neisseria meningitidis / Q000201:enzymology; D012703:Serotyping; D012794:Sialic Acids / Q000378:metabolism; D013292:Streptococcus agalactiae / Q000201:enzymology* / Q000276:immunology
D012794:Sialic Acids; D003570:Cytidine Triphosphate; D000216:N-Acylneuraminate Cytidylyltransferase; D019158:N-Acetylneuraminic Acid