鲢鱼和草鱼下脚料中CPIs抑制活性比较及其分子量分布的鉴定

本研究首先确定偶氮酪蛋白（Azocasein）法和荧光合成肽法测定CPIs抑制活性的适宜反应体系,并证实Azocasein法更适合在鲢、草鱼下脚料（卵、皮）粗提过程中监测CPIs的抑制活性,而在层析过程中需采用高灵敏度的荧光合成肽法。Azocasein法测定表明,草鱼卵（349600units、332units/mg）和皮（25600units、87units/mg）中总活和比活均分别显著高于鲢鱼卵（10620units、3.98units/mg）和皮（3726units、14.14units/mg）;同时,草鱼卵中CPIs抑制总活、比活均高于皮;鲢鱼卵中CPIs抑制总活高于皮,但抑制比活则低于皮;此外,根据Sephacryl S-200分子筛层析中活性峰位置,初步判断两种鱼卵和皮组织中均存在高（50¹28ku）、低（7¹9ku）分子量形式的CPIs,但明胶底物-SDS-PAGE反相酶谱中仅可见高分子CPIs形成的条带,而小于20ku的低分子CPIs均无法得到鉴定。 

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.