Digestive proteases from wild and farmed male morphotypes of the Amazon river prawn (Macrobrachium amazonicum)

Abstract

The aim of this study was to characterize digestive proteases from wild and farmed morphotypes in males of Macrobrachium amazonicum (Heller, 1862). The hepatopancreas of wild and earthen pond reared specimens were collected and homogenized. Unspecific activities of trypsin, chymotrypsin and leucine aminopeptidase were determined using specific substrates. Serine-protease, trypsin, and chymotrypsin specific inhibitors were employed to assess enzyme inhibition. Optimum pH, temperature and thermal stability of the enzymes were also evaluated. Complementary study was carried out using electrophoresis and zymograms. Proteolytic activities were higher in farmed than in the wild prawns and differences were observed among the farmed male morphotypes, while no differences were observed in the wild ones. Both farmed and wild specimens showed similar values of amylase:protease ratio ranging from 0.06 to 0.12. Inhibition assays revealed the presence of serine proteases, trypsin, and chymotrypsin in the hepatopancreas. However, stronger trypsin inhibitions occurred in farmed morphotypes. The optimum temperature and pH were 65°C and 8.0 to 8.5, respectively. Electrophoresis revealed bands between 6 kDa and 205 kDa. Zymograms revealed bands with proteolytic activity. Using the wild animals as a reference, the results suggest that digestive proteases profile changes in farmed prawns, which may be an adaptation to the culture conditions.