酱油曲蛋白酶的分离及催化性质研究

Study on isolation and catalysis property of proteases in koji of soy sauce

酱油曲提取液,经硫酸铵盐析后,用Sephadex G-75柱层析分离,测定收集液中的蛋白含量并用两种方法测定蛋白酶活力。结果显示,福林法酶活力峰出现在蛋白吸收曲线第二高峰,酶解酪蛋白显示的酶活力峰值出现在蛋白含量第三高峰的左肩。表明酱油曲含有不同分子量大小的蛋白酶,分别作用于蛋白质的不同位点,分子量较大(在20 kDa到14.3 kDa之间)的蛋白酶福林法酶活力最高,蛋白酶水解酪蛋白产生的酪氨酸较多;分子量比较小(小于14.3 kDa)的蛋白酶福林法检测酶活力不高,但分解酪蛋白产生的氨基酸态氮(ANN)含量较高,表明该蛋白酶酶解酪蛋白产生酪氨酸之外的其它氨基酸或肽类较多。

The proteases extracted from soy sauce koji were salted out by solution and isolated by Sephadex G-75 gel. The protease activity of the ammonium sulfate saturated collection were determine re spectively by the method of Folin and the method measuring total amino acid nitrogen （AAN）. It shows that there are different kinds of protease in the koji and they act on different points of the pep- tide chain. The peak of protease activity tested by Folin is at the second high peak of the curve, which Molecular Weight（MW） is between 20 kDa and 14.3 kDa. The tyrosine content is higher in product of hydrolysis when acts on the casein with this collection. The peak of protease activity test by ANN is at the left shoulder of the third peak, which MW is lower than 14.3 kDa. The tyrosine content is less when it acts on casein, but there are more other kinds of amino acids and polypeptides in the product of hydrolysis.