This enzyme is a serine protease capable of degrading the native triple helix of collagen. Also cleaves the B chain of insulin at the 15-Leu-|-Try-16 and 22-Arg-|-Gly-23 bonds. Hydrolyzes casein, but not Px-Pro-Leu-Gly-Pro-DArg, BzArgNHPh, AcTyrNHPh, 2-naphthyl phosphate, 2-naphthyl butyrate, 2-naphthyl caprylate, 2-naphthyl myristate, L-leucine 2-2-naphthylamide, L-valine 2-naphthylamide, L-cysteine 2-naphthylamide or L-glutarylphenylalanine 2-naphthylamide. Hydrolysis of proteins including native collagen at Xaa-|-Ala bond leaving an N-terminal (75%) and a C-terminal (25%) fragment. Inhibited by diisopropylfluorophosphate. Optimum pH is 8.0-8.5. Reversibly inactivated below pH 4.5. Thermostable. No loss of activity occurs after incubation for 2 hours at 60 degrees Celsius. Inactivated after incubation for 2 hours at 75 degrees Celsius, however 45% of activity remains after incubation for 20 minutes at 75 degrees Celsius. Larval-specific. Belongs to the peptidase S1 family.