Digestive proteinases and peptidases in the hepatopancreas of the southern brown shrimp (Farfantepenaeus subtilis) in two sub-adult stages

The aim of this study was to examine proteinases and peptidases from the hepatopancreas of two sub-adult stages of Farfantepenaeus subtilis: SAS(6) (5.93 +/- 0.69 g wet weight) and SAS(13) (13.26 +/- 0.60 g wet weight). Trypsin and chymotrypsin activity was higher in the extract from the SAS(6) individuals (P < 0.05). The highest activity among aminoacyl-beta-naphthylamide substrates was found using alanine-, arginine-, leucine- and lysine-beta-naphthylamide. There was a positive correlation between the recommended concentration of essential amino acids in penaeid shrimp feed and aminopeptidase activity in both sub-adult stages. Proteolytic activity of F. subtilis was strongly inhibited by specific trypsin inhibitors. The optimal temperature for trypsin, chymotrypsin and leucine aminopeptidase activity was between 45 and 55 degrees C. Six and seven bands were found in caseinolytic zymograms for SAS(6) and SAS(13) respectively. All bands were inhibited by phenylmethylsulfonyl fluoride in both sub-adult stages. The use of tosyl-lysine-chloromethyl-ketone and benzamidine caused strong inhibition of the proteolytic bands. Trypsin and chymotrypsin activity was the main difference observed between the protease pattern of SAS(6) and SAS(13)F. subtilis.