INITIAL CHARACTERIZATION OF SUCROSE-6-PHOSPHATE HYDROLASE FROM STREPTOCOCCUS-MUTANS AND ITS APPARENT IDENTITY WITH INTRACELLULAR INVERTASE

An intracellular enzyme catalyzing the hydrolysis of sucrose-6-phosphate to glucose-6-phosphate and fructose has been identified in extracts of Streptococcus mutans 6715-10. The preparation was purified chromatographically and found to have an apparent molecular weight of 42,000. The enzyme has as a Km for sucrose-6-phosphate of 0.21 mM, a pH optimum of 7.1, is quite stable and requires no added cofactors or metal ions. Sucrose is a competitive inhibitor of sucrose-6-phosphate hydrolysis (Ki = 8. 12 mM). A previously described intracellular invertase copurifies with the enzyme and could not be separated from it by disc gel electrophoresis. It is concluded that intracellular invertase is a sucrose-6-phosphate hydrolase with a low catalytic activity for hydrolysis of sucrose. © 1979.