表面活性剂稳定性碱性蛋白酶纯化及性质研究

Purification and Characterization of Surfactant-stable Protease

从地衣芽孢杆菌(Bacillus licheniformis)XG12发酵液中分离纯化表面活性剂稳定性碱性蛋白酶,并对酶学性质进行研究。利用硫酸铵分级盐析、DEAE-Sepharose阴离子交换层析和Sephadex G-75分子筛凝胶过滤层析等方法,分离纯化到了均一的酶蛋白,酶纯度提高了42.6倍,回收率为25.3%。SDS-PAGE及Sephadex G-75分子筛凝胶过滤层析显示酶蛋白为单亚基蛋白,分子质量约为29.5kD。在pH7.0～11.0范围内酶活性及稳定性较高,最适作用pH值为10.0,最适作用温度40℃。Mg2+、Ca2+及Mn2+对酶有明显激活作用。丝氨酸蛋白酶特异性抑制剂强烈抑制酶活性,表明所纯化到的蛋白酶为丝氨酸蛋白酶。酶分别对终质量浓度为0.1g/100mL的阴离子表面活性剂SDS、阳离子表面活性剂CTAB和体积分数为1%的非离子型表面活性剂Tween-80、Tween-20、Triton X-100以及氧化剂均具有很强的稳定性。

A surfactant-stable alkaline protease was isolated and purified from Bacillus licheniformis XG12,and its enzymatic properties were also characterized.A protease with high purity from strain XG12 was purified by precipitation with ammonium sulfate,DEAE-Sepharose ion exchange chromatography and Sephadex G-75 gel filtration chromatography.The purified protease exhibited a 42.6-fold enhancement in specific activity and its recovery rate was 25.3%.The enzyme was composed of a single polypeptide chain with an apparent molecular mass of 29.5 kD as determined by SDS-PAGE.This alkaline protease was highly active and stable in the pH range of 7.0-11.0 with an optimal pH of 10.0.The maximum activity of this alkaline protease was observed at 40 ℃.In addition,this protease could be activated by divalent cations such as Mg2＋,Ca2＋ and Mn2＋ and inhibited by serine-protease inhibitors,suggesting that this alkaline protease was a serine-protease.Moreover,this alkaline protease also exhibited extreme stability towards anionic（0.1% SDS）,cationic（0.1% CTAB）,non-ionic surfactants（1% Tween-80,1% Tween-20 and 1% Triton X-100） and oxidants.Due to its promising properties,this alkaline protease from Bacillus licheniformis XG12 will have potential applications in food and laundry detergents.