TAILIEUCHUNG - Báo cáo Y học: Thermodynamics and kinetics of the cleavage of DNA catalyzed by bleomycin A5 A microcalorimetric study

Microcalorimetry and UV-vis spectroscopy were used to conduct thermodynamic and kinetic investigations of the scission of calf thymus DNA catalyzed by bleomycin A5 (BLM-A5) in the presence of ferrous ion and oxygen. The molar reaction enthalpy for the cleavage, the Michaelis– Menten constant for calf thymus DNA and the turnover number of BLM-A5 were calculated by a novel thermokinetic method for an enzyme-catalyzed reaction to be )577 ± 19 kJÆmol)1, ± lM and ± · 10)2 s)1, respectively, at °C. This DNA cleavage was a largely exothermic reaction | Eur. J. Biochem. 269 2851-2859 2002 FEBS 2002 doi Thermodynamics and kinetics of the cleavage of DNA catalyzed by bleomycin A5 A microcalorimetric study Yi Liang1 Fen Du1 Bing-Rui Zhou1 Hui Zhou1 Guo-Lin Zou1 Cun-Xin Wang2 and Song-Sheng Qu2 1 College of Life Sciences and 2College of Chemistry and Molecular Science Wuhan University China Microcalorimetry and UV-vis spectroscopy were used to conduct thermodynamic and kinetic investigations of the scission of calf thymus DNA catalyzed by bleomycin A5 BLM-A5 in the presence of ferrous ion and oxygen. The molar reaction enthalpy for the cleavage the Michaelis-Menten constant for calf thymus DNA and the turnover number of BLM-A5 were calculated by a novel thermoki-netic method for an enzyme-catalyzed reaction to be -577 19 kJ-mol-1 IM and X 10-2 s-1 respectively at C. This DNA cleavage was a largely exothermic reaction. The catalytic efficiency of BLM-A5 is of the same order of magnitude as that of lysozyme but several orders of magnitude lower than those of TaqI restriction endonuclease Nael endonuclease and BamHI endonuclease. By comparing the molar enthalpy change for the cleavage of calf thymus DNA induced by BLM-A5 with those for the scission of calf thymus DNA mediated by adriamycin and by 1 10-phenanthroline -copper it was found that BLM-A5 possessed the highest DNA cleavage efficiency among these DNA-damaging agents. These results suggest that BLM-A5 is not as efficient as a DNA-cleaving enzyme although the cleavage of DNA by BLM-A5 follows Michaelis-Menten kinetics. Binding of BLM-A5 to calf thymus DNA is driven by a favorable entropy increase with a less favorable enthalpy decrease in line with a partial intercalation mode involved in BLM-catalyzed breakage of DNA. Keywords bleomycin DNA cleavage kinetics microcalorimetry thermodynamics. The bleomycins BLMs Fig. 1 are a family of naturally occurring structurally related glycopeptide-derived antitumor .

• Báo cáo khoa học
• Report medicine
• traditional medicine
• scientific reports
• breast cancer
• biological activities
• gastric cancer
• medical knowledge
• medical research
• analysis of cytoplasmic
• oxidation
• Crystal structure
• bacteria
• hemoglobin
• medicine
• cell proliferation
• chemical reaction
• hormone medicine
• tumor cells
• biochemical studies
• environmental medicine