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다형핵의 백혈구에 의한 Isocitrate dehydrogenase 산화계의 역활

다형핵의 백혈구에 의한 Isocitrate dehydrogenase 산화계의 역활
Other Titles
(The) Myeloperoxidase-Hydrogen Peroxide-Halide System as Effector of Polynorphonuclear Leukocytes-Mediated Ina-ctivation of Isocitrate Dehydrogenase
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대학원 약학과
다형핵백혈구불활성화Isocitrate dehydrogenase 산화계
이화여자대학교 대학원
다형핵 백혈구(PMNs)는 phorbol ntyristate acetate(PMA)로 자극되면 O_(2)^(-)·와 H_(2)O_(2)를 생성하며 isocitrate dehydrogenase(ICDH)를 불활성화 시켰다. 이때 효소의 불활성화는 catalase에 의해서는 억제되었으나 superoxide dismutase에 의해서는 영향이 없었다. 또한 불활성화는 myeloperoxidase(MPO) 억제제인 azide와 ^(1)O_(2)의 제거물질 (DABCO와 histidine) 및 HOC1제거물질 (serine과 valine)에 의해서도 억제되었다. 반면 OH·의 제거물질 (mannitol, benzoate와 formate)과 Fe^(++) 및 EDTA에 의해서는 영향이 없었다. 또한 Fe^(++)는 azide 존재 시 에서 조차 주목할 만한 영향이 없었다. PMNs는 halide가 존재하지 않는 조건에서도 PMA로 자극될때 O_(2)^(-)·와 H_(2)O_(2)는 생성시키나 효소는 불활성화 시키지 못 하였다. 그러나 이 반응액에 halide(Cl^(-), Br^(-), I^(-))첨가로 효소는 불활성화 되었다. 이 효소를 cell-free MPO-H_(2)O_(2)-halide 산화계로 처리하였을때도 불활성화 되었으며, 이때 azide나 ^(1)O_(2) 및 HOCl의 제거물질의 첨가 또는 반응액 중 halide를 제거하였을 때는 불활성화 되지 아니하였다. 이와 같은 결과들로부터 ICDH가 MPO 산화계에 의하여 불활성화 되었음을 알 수 있으며 따라서 MPO산화계가 PMNs으로 매개되는 산소 의존성 파괴작용의 주요 기전으로 사료되었다.;Polymorphonuclear leukocytes(PMNs) when stimulated by phorbol myristate acetatet(PMA) produced O_(2) and H_(2)O_(2) and were able to inactivate isocitrate dehydrogenase. The enzyme inactivation was prevented by the addition of catalase, but no effect was found with superoxide dismutase. The inactivation was also prevented by azide, an inhibitor of rnyeloperoxidase or quenchers for (1)^O_(2)(ABCO and histidine) and HOCl(serine and valine). On the other hand, OH·quenchers(mannitol, benzoate and formate) had no effect on the inactivation. Futhermore the inactivation was not affected by the addition of Fe^(++) or EDTA. Effect of Fe^(++) was not significant even in the presence of azide. When PMNs were stimulated in the halide-omitted medium, the enzyme was not inactivated, although the rates of □ and H_(2)O_(2) productions were the same with those observed in the halide-containing medium. However the inactivation was demonstrated by adding halides(Cl^(-), I^(-) or Br^(-)) to the medium. When isocitrate dehydrogenase was incubated with cell-free myeloperoxidase-H_(2)O_(2)-halide system, the enzyme was inactivated. The inactivation was also prevented by azide, quenchers for (1)^O_(2) and HOCl or omission of halides from the medium. The findings observed indicate that isocitrate dehydrogenase was inactivated by the action of myeloperoxidase-H_(2)O_(2)-halide system. Thus, it appears that the rnyeloperokidase system serves as a major mechanism in PMNs-mediated oxidative toxic actions.
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