摘要
A series of experiments based on electrophoretical and biochemical assays were conducted to partially characterize proteinases present in the hepatopancreas and intestine of black carp （Mylopharyngodon piceus）, and investigate enzymatic activity and protein digestibility in vitro. Casein digestion assays revealed the presence of acidic proteinases with optimum activity in the range of pH 2.0-2.5 and alkaline proteinases with significantly higher activities both in the range of pH 8.1-8.6 and near pH 9.5. The inhibition and substrate specificity assays showed that trypsin and chymotrypsin are the main active components of the alkaline proteinases. The SDS-substrate-PAGE showed that the crude extract of black carp intestine had eight types of alkaline proteinases with the molecular mass range of 27.5-78.5 kDa while the crude extract of black carp hepatopancreas had six types of alkaline proteinases with the molecular mass range of 27.5-78.5 kDa. These enzymes were characterized as trypsin （27.5 kDa, 30.1 kDa）, chymotrypsin （40.5 kDa, 42.5 kDa）, serine proteinases （32.1 kDa, 33.2 kDa） and non-serine proteinase （61.5 kDa, 78.5 kDa）.In vitro protein digestibility assays showed that black cardcan be able to utilize a wider range of proteins.
