Characteristics of the protease from the extreme halophile, Halobacterium sp.

고도 호염성 Halobacterium sp.가 생산하는 protease의 특성

The pretense from Halobacterium sp. was purified by ethanol precipitation and gel filtration on Sephadex G-75 and G-100. The purified enzyme was found to be homogeneous by polyacrylamide gel electrophoresis It's specific activity was 364units/mg protein and yield was 14% of the total activity of the culture filtrate. The Km value against casein was determined to be $4.2{\times}10^{-4}M$ by Lineweaver-Burk plot The optimal temperature and pH for the enzyme activity were $35^{\circ}C$ and pH 8.0, respectively. The enzyme was stable from 5.0 to 11.0 at relatively wide range of pH but was inactivated at the temperature above $50^{\circ}C$. $Ca^{2+}$ and $Mg^{2+}$ appeared to react as activators whereas $Fe^{3+},\;Zn^{2+},\;Cu^{2+},\;Hg^{2+}\;and\;Cd^{2+}$ as inhibitors. The enzyme activity reduced with increasing the concentration of NaCl : the apparent activity with 2M NaCl was 65% as compared with that without the salt However the enzyme was unstable without salts : the activity was lost when dialyzed against distilled water for 2hr, whereas maintained against 0.1M solution of $CaCl_2$ for 6hr.

Halobacterium sp.가 생산하는 protease를 ethanol 침전, S데hadexG-100 및 G-75로 겔 여과하여 비활성이 364units/mg protein 수율이 14%로 정제할 수 있었다. 정제호소의 casein에 대한 Km값은 $4.2{\times}10^{-4}M$이었다. 이 효소의 반응 최적온도 및 pH는 $35^{\circ}C$와 pH 8.0이었고, 온도 및 pH에 대한 안정성은 $50^{\circ}C$까지와 pH $5.0{\sim}11.0$범위이었다. $Ca^{2+}$와 $Mg^{2+}$ 이온은 효소의 활성을 증가시켰고 $Fe^{3+},\;Zn^{2+},\;Cu^{2+},\;Hg^{2+},\;Cd^{2+}$ 이온은 저해하였다. 정제호소는 기질용액중에 NaCl농도가 증가함에 따라 효소활성이 감소하고 2M NaCl 농도 이하에서 투석하면 활성이 저하되었으며 증류수로 2시간 투석으로 완전히 실활되었다. 그러나 0.1M $CaCl_2$용액으로는 6시간 투석하여도 활성은 그대로 유지되었다.