PROTEIN DIGESTION IN THE EUROPEAN LOBSTER, HOMARUS-GAMMARUS (L)

Protease activity from extracts of the stomach and hepatopancreas of t he European lobster have been examined and compared. pH Activity profi les for hydrolysis of casein were similar for both extracts with optim al action at pH 2.3 and 5.8. The extracts of the hepatopancreas contai ned endoproteases-elastase (EC 3.4.21.36), trypsin (EC 3.4.21.4) and e xoproteases-leucine aminopeptidase (EC 3.4.11.1) and carboxypeptidases a (EC 3.4.17.1) and carboxypeptidase b (EC 3.4.17.2), It was not poss ible to detect any chymotrypsin (EC 3.4.21.1) activity. The acidic pro tease activity (optimal at pH 2.3) did not hydrolyse N-acetyl phenylal anyl di-iodotyrosine (a pepsin-specific substrate) nor was the action at acid pH inhibited by the pepsin specific inhibitor pepstatin A. The physiological significance of this protease action at acid pH values is in doubt since it is not observed in other crustaceans nor was it d etected in parallel experiments on whole gut extracts of the shrimp Pe naeus monodon.