Characteristics of the RNase from the moderate halophile, Micrococcus sp.

호염성 세균 Micrococcus Sp.가 생산하는 RNase의 특성

The halophile, Micrococcus sp. which produces RNase was isolated from salted and fermented food. The optimum growth condition of the Micrococcus sp. in pH 7.0 of complex medium containing 2M NaCl, and at $35^{\circ}C$. Optimum condition for enzyme production by this strain was when it was grown in the CM medium, containing 2% yeast extract, 1.5% casamino acid and 2M NaCl in the initial pH 8.5 for 2 days. The maximal RNase activity was observed at pH 8.0 and $55^{\circ}C$. The Km value for RNA was determined to be 5mg/ml by Lineweaver-Burk plot. The RNase activity in the absence of NaCl was maximum, but it was completely lost by adding of 1.25M NaCl and it was increased above 1.25M to 2.5M NaCl. When 2.5M NaCl was added, the activity of RNase showed 45% of maximum value.

RNase를 강하게 분비하는 균을 젓갈류서 분리하여 호염성 Micrococcus sp.로 동정하였다. 선정균은 NaCl을 2M 함유하는 pH 7.0의 CM배지에서 $35^{\circ}C$로 2일간 배양할 때 생육이 가장 양호하였으며 yeast extract 2.0%, casamino acid 1.5%, NaCl 2.0M, pH 8.5의 배지에서 $35^{\circ}C$로 2일간 배양할 때 효소 생산이 최대였다. 조효소액을 유안 염석과 이온교환 크로마토그라피, gel 여과 등으로 정제한 결과 비활성이 98.8 units/mg, 정제도는 39.4배, 수율은 0.9% 이었다. 정제 효소의 작용 최적 pH는 8.0, 온도는 $55^{\circ}C$이었으며 RNA를 기질로 한 Km값은 5mg/ml이었다. NaCI농도에 따른 효소활성은 무첨가조건에서 가장 높았고 1.25M에서 활성이 소설되었다가 다시 증가되어 2.5M에서는 무첨가구의 45% 활성을 보였다.