Streptomyces subrutilus P5의 천연 Fe superoxide dismutase와 N-말단 6xHis-태그가 결합된 Fe superoxide dismutase의 활성비교 = Comparison of enzyme activities of the native and N-terminal 6xHis-tagged Fe supreoxide dismutase from Streptomyces subrutilus P5

국문 초록 (Abstract)

본 연구는 Streptomyces subrutilus P5의 천연 Fe superoxide dismutase (FeSOD)와 유전자 재조합 기술로 생산된 6xHis-태그가 결합된 Fe superoxide dismutase (6xHis- FeSOD)의 활성을 비교하여 6xHis-태그의 효소에 대한 영향을 알아보기 위하여 수행되었다. 두 효소 모두 최적 pH는 7로 동일하였으나 6xHis-태그에 의해서 pH 범위는 축소되었다. 천연 효소는 pH 4-9의 범위에서 안정성을 보인 반면 6xHis-FeSOD는 pH 9에서 안정성이 상실되었다. 두 효소의 최적 온도는 차이가 없으나 열 안정성에 있어서는 천연 효소는 $40^{\circ}C$ 이하에서 720분까지 안정성을 유지하였으나 6xHis-FeSOD는 $20^{\circ}C$에서도 360분 이내에 활성을 잃는 것으로 나타났다. $H_2O_2$의 6xHis-FeSOD에 대한 저해는 0.5 mM에서 나타났다. 따라서 6xHis-FeSOD는 효소활성은 유지되더라도 열 안정성이 크게 감소되는 결과를 얻었다. 이것은 6xHis-태그가 활성부위 보다는 단백질 전체 구조에 더 많은 영향을 미친 결과라고 생각되었다.

다국어 초록 (Multilingual Abstract)

This study was carried out to analyze the differences in enzyme activity and stability between the native Fe superoxide dismutase (FeSOD) and the 6xHis-tagged superoxide dismutase (6xHis-FeSOD) of Streptomyces subrutilus P5. The optimum pHs for both native FeSOD and 6xHis-FeSOD were 7, while the pH range of the activity was narrower for the 6xHis-FeSOD. The native FeSOD was stable at pH 4-9, but the 6xHis-FeSOD lost its stability at pH > 9. The temperatures of the optimum activities were same for both types of enzymes. However, the heat stability of the 6xHis-FeSOD was clearly decreased; even at $20^{\circ}C$ the enzyme lost the activity after 360 min. In contrast, the native FeSOD was stable after 720 min at below $40^{\circ}C$. $H_2O_2$ inhibition was occurred already at 0.5 mM for the 6xHis-tagged enzyme. Therefore, from the results that the 6xHis-FeSOD retained the enzyme activity at pH 6-7 and $20-40^{\circ}C$, it can be assumed that the protein structure became destabilized under different storage conditions and sensitive to the enzyme inhibitor.

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