Hydrolysis of proteins with broad specificity similar to that of pepsin A, preferring hydrophobic residues at P1 and P1'. Clots milk and activates trypsinogen. Does not cleave 4-Gln-|-His-5, but does cleave 10-His-|-Leu-11 and 12-Val-|-Glu-13 in B chain of insulin. Optimum pH is 7 with hemoglobin as substrate. Optimum temperature is between 45-50 degrees Celsius with hemoglobin as substrate. Loses 50% of its activity at 60 degrees Celsius. This enzyme is capable of clotting milk and thus can be used for cheese production. Belongs to the peptidase A1 family.