Chymotrypsin from shrimp, Penaeus californiensis, was compared to Bos taurus chymotrypsin, and its structure–function relationship was studied. Catalytic efficiency toward synthetic substrate is lower, but it has a broad specificity and higher activity toward protein substrates, including collagen. It is active at pH 4–10 and fully active up to 50 C for 2 h and at least nine days at room temperature.