a zinc-endopeptidase from the crayfish Astacus astacus & Hydra vulgaris; releases nitroaniline from succinyl-alanyl-alanyl-alanyl-4-nitroanilide (Suc-Ala-Ala-Ala-pNA); acts on peptides containing 5 or more amino acids, preferably with ALA in P1' and Pro in P2'