title: Protease activity in gut of Daphnia magna: evidence for trypsin and chymotrypsin enzymes.
abstract: Two major protease activities were present in gut homogenates of the cladoceran crustacean Daphnia magna: (i) a trypsin activity that hydrolysed the synthetic substrate N-benzoyl-dl-arginine p-nitroanilide and was strongly inhibited by N-p-tosyl-lysine chloroketone (TLCK) and 4-(amidinophenyl)methanesulfonyl fluoride (APMSF) and not inhibited by chymostatin; and (ii) a chymotrypsin activity that hydrolysed synthetic chymotrypsin substrates containing more than one amino acid, did not hydrolyse N-benzoyl-l-tyrosine p-nitroanilide, and was strongly inhibited by chymostatin and not by TLCK and APMSF. Both activities had alkaline pH optima (pH 7-10), but were shown to be due to distinct types of proteases. These two enzyme activities accounted for 75-83% of the proteolytic activity of gut contents. Substrate SDS-polyacrylamide gel electrophoresis revealed nine different proteases ranging from 15 to 73 kDa.
authors.affiliation: Limnological Institute, University of Constance, 78434 Konstanz, Germany. eric.vonelert@uni-konstanz.de
authors.forename: Eric
authors.initials: E
authors.lastname: von Elert
authors.forename: Manish Kumar
authors.initials: MK
authors.lastname: Agrawal
authors.forename: Christine
authors.initials: C
authors.lastname: Gebauer
authors.forename: Heike
authors.initials: H
authors.lastname: Jaensch
authors.forename: Ulrike
authors.initials: U
authors.lastname: Bauer
authors.forename: Anja
authors.initials: A
authors.lastname: Zitt
mesh_terms: D000818:Animals; D001586:Benzoylarginine Nitroanilide / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D003621:Daphnia / Q000201:enzymology*; D004063:Digestion; D017753:Ecosystem; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000201:enzymology*; D011480:Protease Inhibitors / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000378:metabolism*; D013379:Substrate Specificity; D014357:Trypsin / Q000378:metabolism
chemical_list: D011480:Protease Inhibitors; D001586:Benzoylarginine Nitroanilide; D012697:Serine Endopeptidases; D002918:Chymotrypsin; D014357:Trypsin