백서 재생간의 DNA topoisomerase Ⅰ 에 관한 연구 = Studies on DNA topoisomerase Ⅰ from regenerating rat liver

다국어 초록 (Multilingual Abstract)

The study was performed to evaluate changes of activity of DNA topoisomerase I that controls and modifies the topological state of DNA according to postoperative days after partial hepatectomy.
The results of this experimental study were summarized as follows :
1. The liver mass doubles during the first 48 hours, and the rate of regeneration is greatest between first and second days after partial hepatectomy.
2. 25% of enzyme activity was increased in the first 12 hours in comparison with that of control after partial hepatectomy. The second days showed maximal increment. 200% in comparison with that of control. Later, enzyme activity was decreased till the seventh days after partial hepatectomy.
3. DNA Topo I was inhibited very slightly be camptothecin but 50% of enzyme activity was inhibited at 50μM of 10-hydroxycamptothecin.
4. In the case of spermine. 0.1mM. Complex formation was highest as 0.1mM spermine.
5. The enzyme shows a pH optimum around 6.4, but enzyme activity is seen within a broad range between pH 5.8 and 9.0.
6. The enzyme is completely inactivated by heat treatment for 5 minutes at 50℃.
7. 2mM Mg^2+ activates the enzyme activity over 3-folds. Cu^2+, Zn^2+ completely inhibit it and Mn^2+, Co^2+, and Se^2+ inhibit upto 40%, 40% and 60% at 2mM respectively.
8. There was no sighificant difference between resection and regeneration liver.
These results suggested that the role of DNA topoisomerase I is related to 2nd peak of DNA synthesis in regeneration of liver after partial hepatectomy.