酸性条件下毛霉和根霉蛋白酶的催化特性

摘要

研究比较了Actinomucor elegans蛋白酶和Rhizopus oligosporus蛋白酶在pH 3.0～6.0的条件下催化大豆分离蛋白（SPI）降解的特性,结果表明：在pH3.0和pH3.5的条件下,SDS-PAGE显示毛霉和根霉蛋白酶都能迅速地催化大豆7S和11S蛋白的降解,但此时水溶性蛋白的得率不高,均在35%以下;在pH5.0、5.5和6.0时,毛霉和根霉蛋白酶催化大豆分离蛋白降解的能力增强,水解度升高,水溶性蛋白的得率增加,但毛霉蛋白酶的水解产物水溶性蛋白得率始终高出约10%,SDS-PAGE显示毛霉蛋白酶催化下的大豆分离蛋白各个亚基降解消失的速度下降,同时伴随有新的条带产生,特别是碱性亚基几乎不能在4h内降解,根霉蛋白酶催化下的大豆分离蛋白各个亚基降解消失的速度在pH5.0和5.5时还比较强,但在pH6.0时明显下降,酸性亚基和碱性亚基均不能在4h内消失,表明在酸性条件下2个霉菌的蛋白酶其催化特性有明显的差异。%Proteolysis of soybean protein isolated（SPI） by A.elegans and R.oligosporus proteases,which were cultured in their optimal enzyme production conditions,under acidic conditions pH3.0～6.0 was investigated.The results showed that,A.elegans and R.oligosporus proteases were able to quickly catalytic soybean 7s and 11s protein degradation when pH was 3.0～3.5,but at the moment,water - soluble protein yield were not high,all under 35%. At pH5.0,5.5 and 6.0,A.elegans and R.oligosporus protease all had stronger catalytic ability of degradation of SPI,both the hydrolysis degree and water-soluble protein increased,but the water - soluble protein yield from A.elegans had always been about 10%higher.SDS - PAGE showed the catalytic rate of A.elegans protease to soybean protein isolated reduced,and appeared with new bands,especially basic subunits was not able to be degraded in four hours.The speed of R.oligosporus protease catalytic degradation of soybean protein isolated was still stronger at pH5.0 and 5.5,but declined obviously at pH6.0,The acidic subunits and basic subunits were not degraded in four hours.In a word,there had big differences between the two proteases on catalysis characteristics at acidic condition.