EXTRACELLULAR PROTEINASE OF STREPTOCOCCUS LACTIS.

Williamson, W. T. (North Carolina State of the University of North Carolina, Raleigh), S. B. Tove, and M. L. Speck. Extracellular proteinase of Streptococcus lactis. J. Bacteriol. 87:49-53. 1964.-Streptococcus lactis was shown to produce an extracellular proteolytic enzyme(s). A 120-fold purification of the proteinase was obtained from the cell-free culture medium by ammonium sulfate fractionation, calcium phosphate gel treatment, and chromatography on diethylaminoethyl cellulose. Only 32% of the activity was destroyed by heating at 98 C for 1 hr. The requirement of free sulfhydryl groups for enzyme activity was indicated by inhibition with p-chloromercuric benzoate. Diisopropyl fluorophosphate did not inhibit the proteinase.