시안산이 Superoxide Dismutase의 Carbamylation과 활성에 미치는 영향

Abstract

The patients with end stage renal disease show several complications such as artherosclerosis, anemia and increased susceptibility to infection by damage due to oxygen free radicals. Superoxide dismu-tase(SOD) is directly linked to the fate of the highly reactive oxygen metabolites. If there is an alteration in the activity of SOD, this alteration may contribute to the complications by reactive oxygen species in patients with end stage renal disease. In this experiment, SOD activity and the effect of cyanate on the activity of SOD was studied to understand the mechanism of several complications mediated by oxygen free radicals in patients with end stage renal disease. SOD activity in the plasma and erythrocytes from patients with end stage renal disease was significantly lower than those from healthy controls. It is known that underproduction of SOD leads to excess production of superoxide and reduced iron favoring hydroxy 1 radical formation. The results in this experiment suggest that there is an overproduction of superoxide anion in patients with end stage renal disease. The overproduction of superoxide anion may contribute the patients with end stage renal disease susceptible to oxidant damages. To evaluate if cyanate could carbamylate SOD, SOD was incubated with cyanate. The level of carbamylated SOD increased as the time of exposure to cyanate increased from 0 hour to 72 hours. Furthermore, the degree of carbamylation of SOD increased as cyanate concentration in the incubation media rose from 20mM to 1M. There appears to be a maximum degree of carbamylation at a concentration of l.OOOmM cyanate. To test the hypothesis that in vitro carbamylation of SOD alters its biological activity, SOD activity was measured after incubation with cyanateᅳ The activity of carbamylated SOD decreased as the time of exposure to cyanate increased from 0 hour to 72 hours. Furthermore, the activity of carbamylated SOD decreased as cyanate concentration in the incubation media rose from 20mM to 1M and when albumin was added to the reaction mixture, the loss of SOD activity was prevented. These results are consistent with the hypothesis that SOD is also carbamylated and lost biological activity in end stage renal disease patients by cyanate，and that the degree of carbamylation depends on both the concentration of cyanate and the length of exposure. Also, these suggest that albumin may prevent carbamylation of SOD at least in vitro condition.

말기신부전 환자의 혈액 중에서 superoxide dismutase(SOD)의 활성을 측정하여 말기신부전 환자에서 SOD의 활성이 감소되어 있음을 확인하고, 요소가 SOD에 대한 활성 변화에 어떤 역 할을 할 수 있는지를 검토하기 위하여, 시안산과 SOD률 반웅시켜 보았다. 또한 알부민을 침가 하여 시안산에 의한 SOD의 활성 변화에 대한 영향을 관찰하였다. 말기신부전 환자의 혈장 및 적혈구의 SOD의 활성은 정상인에 비해 감소되어 있었다. 500mM 시안산과 SOD를 체온인 37 t에서 반웅시키고 0시간에서 72시간 까지 시간을 경과 시켰을 때, SOD의 활성은 시간이 지남 에 따라 감소되었고 유리 아미노기를 소실하였다. 또한 20mM, 200mM, 500mM 및 1M 시안 산과 SOD를 반응시키고 48시간을 경과 시켰을 때 그 활성도 시안산의 농도가 증가함에 따라 그 활성이 감소하였고 유리 아미노기는 감소하였다. 알부민을 SOD와 시안산의 반응액에 첨가하 였을 때 SOD의 활성 감소가 방지되었다. 따라서 이 연구의 결과 말기신부전 환자에서 시안산은 S이)의 활성올 감소시키는 하나의 요 독으로 작용하리라 생각되며，말기신부전 환자에서 시안산의 농도가 증가되면 중가될수록，또한 시안산의 체내 제거가 늦어져 시안산과 반응 시간이 길면 길수록 SOD는 carbamylation 되어 그 활성은 더욱 더 감소하리라 생각된다. 또한 알부민은 그 작용 기전이 확실치 않지만 SOD의 carbamylation에 영향을 주는 것으로 생각되며 이에 대한 연구가 필요하다고 생각된다.