Effect of arylsulfatase A and sialidase on the biochemical and immunological properties of creatine kinase isoenzyme BB.

This work describes the action of the lysosomal enzymes arylsulfatase A (EC 3.1.6.1) and sialidase (EC 3.2.1.18) on human creatine kinase (CK, EC 2.7.3.2) isoenzyme BB. The isoenzyme, which gives a positive reaction with the periodic acid-Schiff reagent, contains 12 molecules of sulfate and two molecules of sialic acid per molecule. On treatment with arylsulfatase, CK-BB lost enzyme activity but retained immunoreactivity, its isoelectric point was altered, and it was partly bound to a "Glyco-gel" affinity column. On treatment with sialidase, the isoenzyme lost activity, its immunoreactivity was decreased by 70%, and the inactivated CK-BB would not bind to either "Glyco-gel" or concanavalin A. We propose that the sulfate groups are involved in maintaining the integrity of the active site of the enzyme but are not involved in antigenic recognition sites on the molecule. Sialic acid plays an important role in both the structural pattern of the antigenic determinant and the active site of CK-BB.