Purification and Properties of Intracellular Proteinase from Streptococcus cremoris

Proteolytic activity in the extract from the cells of Streptococcus cremoris increased in the presence of casein, lactose, glucose, and CaCl(2) in the media but was negligibly detectable in the extract of the cells harvested from the culture containing succinate or citrate. The intracellular proteinase from S. cremoris harvested from tomato medium was purified 150-fold in this experiment. The enzyme had a molecular weight of 140,000, optimum pH at 6.5 to 7.0, and maximum activity at 30 C. The proteinase was activated by Ca and inhibited by Zn, Cu, Hg, Fe, ethylenediaminetetraacetate, and sodium lauryl sulfate. The K(m) value of the enzyme towards each casein fraction was almost the same, and the V(max) of the enzyme towards alpha(s)-casein was smaller than those towards the other casein fractions.