Comparative study on three electrophoresis methods for identifying silver carp CPIs

In this study, three methods, the Geltain-substrate-SDS-PAGE reverse zymography ( method A) , Native-PAGE reverse zymography ( method B) and SDS- PAGE after reaction with papain ( method C) , were compared on the aspect of identification effect and sensitivities, so that the optimum way for identifying the CPIs with low molecular weight from silver carp egg extract was determined.The results showed that, for the unstable CPIs liable to inactivation on electrophoresis, method A gave a low sensitivity and false positive phenomenon, and method B could exactly identify the CPIs, but the molecular weight could not be analyzed, whereas method C ( that is, the SDS-PAGE after reaction with papain at 37℃ not less than 5h) obtained effective identification with clear target bands, and provided molecular weight information as well.Although the inhibitive activities of the hepatopancreas extract from silver carp could not be assayed either by fluorescent substrate method or Azocasein method, the existence and molecular weight distribution of the CPIs were identified efficiently by method C. In conclusion, method C or associated with method B was feasible for the identification of CPIs from silver carp wastes.