Streptococcal sialidase. II. Kinetic and immunological studies of sialidase produced by group K streptococcus.

Kinetic and immunological studies were carried out on the sialidase produced by strain 6646, group K streptococcus (K-sialidase). The K(m) values of K-sialidase were 0.9 mm for sialyllactose and 0.17 mm for bovine submaxillary mucin. The antibody against K-sialidase was produced in rabbits immunized with this enzyme. An assay procedure for determination of the anti-K-sialidase activity in terms of reciprocal of the serum dilution corresponding to the 50% inhibition point is described. Anti-K-sialidase activity is widely distributed in human sera, but this has not yet been found to be correlated with streptococcal diseases, and no definite relationship was proved between the anti-K-sialidase titer and the anti-streptolysin O titer through this study. Anti-K-sialidase serum had no effect on Vibrio cholerae sialidase.