An enzyme was purified to homogeneity on a polyacrylamide gel by conventional chromatographic techniques from an extract of Lactococcus lactis ssp. lactis. The molecular weight of the enzyme was estimated to be 140,000, and it was composed of 2 homo subunits. The optimal activity was observed at pH6.0-6.5 and 30-35℃. The enzyme was almost completely stable between pH6.0 and 7.0, and 0 and 40℃. The enzyme seemed to a serine proteinase since it was inhibited by DFP and PMSF. The Km, Vmax and activation enemy of the enzyme for whole casein were 0.044%,1.10μg tyrosine eq./min/mg and 26,300cal/mol, respectively. αs1-and β-casein were degraded to some extent by the enzyme.

An intracellular proteinase has been separated in crystalline from Streptococcus lactis (IAM 1198), and some enzymatic properties of it were studied. The procedure resulting in 45.4-fold purification of the proteinase included protamine sulfate fractionation, DEAE-52 column chromatography and Sephadex G-50 column chromatography. It was purified to a specific activity of 4.72U/mg protein. The proteinase was freezedried, and then dispersed in deionized water containing ethanol to make a proteinase suspension, which was gradually cooled. The enzyme was allowed to be crystallized after storage. Approximately 2% of the original enzyme activity was recovered in the purified fraction. The crystalline proteinase was shown to be homogeneous by polyacrylamide gel electrophoresis. The molecular weight was about 12,500 and the absorption maximum spectrum was at 278nm and the value of E 1% 1cm at 278nm was 10.83. The