사람 대장조직 DNA Topoisomerase I 에 관한 연구 = Studies on DNA Topoisomerase I from Human Colon

다국어 초록 (Multilingual Abstract)

DNA topoisomerase I was prepared from normal mucosa and cancer tissue of human colon and the properties were compared. Specific activity of the enzyme from normal mucosa was 257.2 unit/mg protein/ min and that from cancer tissue was 403 unit/mg protein/min. Both enzymes showed a broad pH optimum from pH 5.8 to pH 7.4 and arc heat-labile, being completely inactivated by heat treatment at 55℃ for 5 minutes. The enzyme from normal mucosa was activated 0.2 M K^+ and 0.15 M Na^+ approximately 20 and 4 folds and that from cancer tissue was activated approximately 40 and 10 folds, respectively. Mg^2+ was the most potent activator, the enzyme from normal mucosa being 5, 20, and 60 folds activated at 2 mM, 10 mM, and 20 mM, respectively and the enzyme from cancer tissue being 2.5, 13, 26 folds activated, respectively. Both enzymes were inhibited by 2 mM ATP and 5 mM GTP in the presence of Mg^2+ and K^+ , respectively. ddATP and ddGTP were the potent inhibitors of these enzymes. The enzvate front nurmal mucosa was activated by spermine, spermidine, and histone H3 and that from cancer tissue was activated by histone H1. The enzyme from normal mucosa yeas completely inactivated by alkaline phosphatase treatment whereas the enzyme activity from cancer tissue was indifferent. The molecular weight of both enzymes were 150 KD. Camptothecin and 10-OH-camptothecin variably inhibited DNA relaxation according to tile enzyme preparation and there was no DNA fragmentation in the cleavage assay.
From the above results, the possible role of phosphorylation for regulation of this enzyme and the application of camptothecin to colon cancer were discussed.