The Biosynthesis of Hyaluronic Acid by Streptococcus

Abstract The mechanism of hyaluronic acid chain growth in a particulate enzyme preparation obtained from Group A Streptococcus has been examined and additional characteristics of the enzyme detailed. Hyaluronic acid chain elongation occurs by the transfer of monosaccharide units from uridine nucleoside diphosphate derivatives to the nonreducing ends of endogenous oligosaccharide. This oligosaccharide which appeared to be chemically identical with hyaluronic acid was released from the enzyme by either acid hydrolysis or digestion with streptococcal hyaluronidase. The only detectable uridine nucleotide product of hyaluronic acid synthesis was UDP, and synthesis was not inhibited by bacitracin. There was no evidence for the participation of lipid-extractable intermediates during hyaluronic acid formation. The pH optimum for polysaccharide formation is 7.1. The enzyme exhibits an absolute dependence upon divalent metal ion and is maximally activated by 10 mm Mg++ or 1 mm Mn++. Michaelis constants for UDP-GlcUA and UDP-GlcNAc are 5 x 10-5 m and 5 x 10-4 m, respectively. The enzyme is inactivated by treatment with 4% 1-butanol. Addition of Mg++ and UDP, UDP-GlcUA, UDP-GlcNAc, or other uridine nucleoside diphosphate sugars prior to butanol treatment prevented inactivation. Fifty per cent stabilization of the enzyme during butanol treatment occurred at 7 x 10-5 m UDP.