Effects of pH. (A) Effects of pH on SCP and BCP activities. (B) Effects of pH on SCP and BCP stabilities. Enzyme activity was tested at various pH using caseine as substrate in the presence of 4 mM CaCl2 at 50°C. The pH stability of the protease was determined by incubating the enzyme in different buffers for 1 h at 4°C and the residual activity was measured at pH 9 and at 50°C for the SCP and at pH 7.5 and at 50°C for the BCP. The activity of the enzyme before incubation was taken as 100%.