Human leucocyte cerebroside sulphate sulphatase.

Some of the properties of the cerebroside sulphate sulphatase of human leucocyte extracts have been studied. The enzyme has an apparent KM of 2.9 mmol/l and is inhibited by the products of the reaction, sulphate and galactocerebroside. A number of divalent metal ions including manganese and magnesium stimulated the reaction only slightly at 5 mmol/l but inhibited strongly at 20 mmol/l. Triton X-100 present in leucocyte extracts also inhibited, increasing both the apparent KM and Vmax. The enzyme activity was dependent on the presence of anionic detergents. At low substrate concentrations a crude taurocholate preparation was the most active of all bile acids examined. Pure taurocholate and sodium cholate were considerably less active. At highter substrate concentrations however, sodium cholate produced the greatest stimulation of enzyme activity. These data suggest that the bile acid/substrate ratio may be a critical factor in determining cerebroside sulphate sulphatase activity at different substrate concentrations.