乳酸菌Enterococcuse faecalis TN-9低温蛋白酶的提纯及性质

对产自乳酸菌Enterococcuze fecalis TN-9的蛋白酶，进行了硫酸铵沉淀，DEAE—Sephadex A-25以及DEAE Cellulofine A-500离子交换层析的3步纯化和特性研究。纯化酶Native PAGE显示1条蛋白带。SDSPAGE和凝胶层析分子量分别为30ku及69ku。纯化酶最适作用温度为30℃，最适作用PH为7．5～8．0，在pH6．0～9．5和45℃以下条件下稳定，在0℃下显示了6．1％的相对活性，60℃以上热处理完全失去酶活。该酶被EDTA-2Na，Hg^2＋、Cu^2＋、Ni^2＋、Ag^2＋、Co^2＋及Pepstatin A不完全抑制。Zn^2＋对蛋白酶具有明显的激活作用。纯化酶作用于偶氮酪蛋白的Km和Vmax分别为0．098％和72mg／（h·mg）。该酶为N末端VGSEVTLKNS的明胶酶（Gelatinase）的一种，性质属于低温蛋白酶。

Purification and Properties of Cold-Adapted Protease from Lactic Acid Bacterium Enterococcus faecalis TN-9

Protease from lactic acid bacterium Enterococcus faecalis TN-9 was purified with three steps, ammonium sulfate precipitation, DEAE-Sephadex A-25, and DEAE Cellnlofine A-500 ion exchange chromatography and studied its properties. Native PAGE analysis of the purified enzyme showed a single protein band. The molecular weight was 30 ku by SDS-PAGE analysis and 69 ku by gel chromatography analysis respectively. The optimal reaction temperature and pH of the enzyme were at 30 ℃ and 7.5 ～ 8.0 respeetively. It was stable at pH 6.0 ～ 9.5 and 45 ℃. Under 0 ℃ it showed 6.1% of relative activity. Heat treatment above 60 ℃ it totally lost its activity. The enzyme was ineomplete-ly inhibited by EDTA-2Na, Hg~(2+) , Cu~(2+) ,Ni~(2+) , Ag~(2+) , Co~(2+) , and Pepstatin. Zn~(2+) had obvious activation to the pro-tease. K_m and V_(max) of the purified enzyme were 0.098% and 72 mg/(h·mg) respectively. The enzyme was one of gelatinase with N-terminal sequence of VGSEVTLKNS. Its property belonged to cold-adapted protease.