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사람 태반조직 DNA Topoisomerase Ⅰ에 관한 연구
이정복,권기량,임규,황병두 ( Jeong Bok Lee,Gi Ryang Kweon,Kyu Lim,Byung Doo Hwang ) 생화학분자생물학회 1992 BMB Reports Vol.25 No.4
DNA topoisomerase I has been purified from human term placenta approximately 520-folds with a 10% yield. The enzyme shows a broad pH optimum from pH 6 to 9 and is heatlabile, being completely inactivated by heat treatment at 50℃ for 5 min. The enzyme is activated by K^+ and Na^+ approximately 20 and 8-folds respectively. Magnesium ion (Mg^(2+)) is the most potent activator, the activity being 20 and 40-folds activated at 2 mM and 10 mM respectively. But copper ion (Cu^(2+)) is a potent inhibitor. In the presence of Mg^(2+) and K^+, the enzyme is inhibited by physiologic concentration of ATP and GTP. Inhibitory mechanism of ATP is considered to be a inhibition of readoptation of active enzyme conformation and that of GTP is to be a inhibition of the prior step of DNA rejoining. The molecular weight is around 68,000. Camptothecin and 10-hydroxycamptothecin inhibit this enzyme, and the inhibitory action of 10-hydroxycamptothecin is potentiated by Mg^(2+) and K^+. DNA fragmentation by 10-hydroxycamptothecin is more potent than that by camptothecin in the DNA cleavage assay. Heparin and Cu^(2+) inhibit the prior step of DNA rejoining by this enzyme. From the above results, the inhibitory action mechanism of ATP, GTP, heparin, Cu^(2+) and the possible role of Mg^(2+) and K^+ for potentiating the inhibitory action of 10-hydroxycamptothecin, and the development the anticancer drug against DNA topoisomerase I as a target enzyme are discussed.
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李正馥,黃炳斗 충남대학교 의과대학 지역사회의학연구소 1985 충남의대잡지 Vol.12 No.2
The elution profile of nonmethylated and endogenous methylated soluble fraction protein of bovine lens are compared by sephacryl S-300 chromatography, and then changes of protein patterns of nonmethylated and methylated α-crystallin fractions have been investigated by urea/polyacrylamide gel electrophoresis. 1. The nonmethylated and methylated soluble fraction proteins are analyzed by sephacryl S-300 chromatography, In the nonmethylated protein four peaks are eluted in the tube No. 21, 30, 34, 38 and identified as α, β_H, β_L, γ-crystallin, but eluted in the tube No. 20, 29, 32, 36 in methylated protein, respectively. 2. When the soluble fraction of lens is methylated with S-adenosyl-L-〔methyl-^3H〕methionine and separated by sephacryl S-300 chromatography, 90% of radioactivity is detected in α-crystallin fraction. 3. Nonmethylated α-crystallin is separated eight subfractions by urea/polyacrylamide gel electrophoresis. In the methylated α-crystallin, subfraction No. 6, 7 are disappeared and No. 4, 5 are increased when compared with that of nonmethylated. From the above result, it is suggested that endogenous methylation of α-crystallin of lens by protein methylase II may be related to the formation of high molecular weight protein.
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白汶基,黃炳斗,李正馥,琴基昌 충남대학교 의과대학 지역사회의학연구소 1978 충남의대잡지 Vol.5 No.1
Properties of alkaline deoxyribonucleases from cytosol and membane fractions of the early human placenta have been investigated. Evidence is indicating that the cytosol deoxyribonuclease (DNase) having an optimal pH around 9 and the plasma membrane bound DNases having an optimal pH around 8 (pH- 8-PM-DNase) and 9. 5 (pH-9.5-PM-DNase), respectively, are distinct enzyme entities. The cytosol DNase, partially purified, is activated by 1mM CO^2+ and the pH-8-PMDNase and the pH-9. 5-PM-DNase are required Mg^2+ and Co2^2+, respectively, for its maximal activity. The cytosol DNase is relatively heat-labile, whereas the plasma membrane bound DNases are heat-labile with some differnce. The above DNases act both on the native DNA and the heat-denatured DNA with preference for the latter. Kinetic analysis shows that the maximal velocity is independent of Co^2+, while Km decreases from 4. 16 × 10 exp(-4) M DNA-p in the absence of Cot^2+ to 9. 4×10 exp(-5) M DNA-p in the presence of Co^2+. From the above result and the fact that the DNA is not only associated with membrane structure, but also membrane-DNA interaction may be relevant to several pathologic process, including aging and carcinogenesis, we discussed that the PH-9-PM-DNase is related to the differenciation of the early placenta.
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