Comparison of CPIs activities and characterization of their molecular weight distributions in the by- products of silver carp and grass carp

In this study, both of two optimal reaction systems for the inhibitive activities assays of CPIs were established respectively with azocasein or fluorescent peptide ( Z- Phe- Arg- MCA) as substance. Then it was verified that the azocasein method was more suitable for monitoring the inhibitory activity of coarse sample prepared from the eggs and the skins of silver carp and grass carp, while the fluorescent peptide method with higher sensitivity appropriate to the chromatography elute.The assay result by azocasein method showed that both the tissues of egg ( 349600 units, 332units / mg) and skin ( 25600 units, 87units / mg) of grass carp had more abundant total activities and specific activity of CPIs than those of silver carp ( egg: 10620 units, 3.98 units / mg, skin: 3726 units, 14.14 units / mg) , and the total activities and the specific activity of CPIs in grass carp egg were higher than those in its skin, but only the total activities in silver carp egg exceeded that in its skin.Moreover, the analysis on Sephacryl S-200 molecular sieve chromatography demonstrated a wide range of molecular weight distribution of CPIs ( 50 ¹28, 7¹9ku) in the tissues of egg and skin of the two fish; However, only the CPIs bands of high molecular weight in the concentrated chromatography elute appeared on the gelatin substrate- SDS- PAGE- reversed phase enzyme spectrometry, all the CPIs less than 20 ku could not be identified.