EXTRACELLULAR PROTEINASE OF STREPTOCOCCUS LACTIS

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Abstract
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.