Hydrolysis of proteins, favoring hydrophobic residues at P1 and P1'. Clots milk. Does not accept Lys at P1, and hence does not activate trypsinogen. Optimum pH is 6 with hemoglobin as substrate. Activity decreases from pH 7, with a 36% decrease in activity when incubated at pH 10. Optimum temperature is between 45-55 degrees Celsius with hemoglobin as substrate. Loses 50% of its activity at 65 degrees Celsius. This enzyme is capable of clotting milk and thus can be used for cheese production. Belongs to the peptidase A1 family.