頁籤選單縮合
題名 | Kinetics of Redox Interaction between Cytochrome C and Thiols=細胞色素-C與硫醇化合物間氧化還原交互作用之動力學研究 |
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作者 | 胡德民; 何善竺; Hu, Teh-min; Ho, Shan-chu; |
期刊 | Journal of Medical Sciences |
出版日期 | 20110600 |
卷期 | 31:3 2011.06[民100.06] |
頁次 | 頁109-115 |
分類號 | 415.13 |
語文 | eng |
關鍵詞 | 細胞色素C; 硫醇化合物; 氧化還原交互作用; Cytochrome c; Glutathione; Cysteine; Thiols; Redox; Kinetics; |
英文摘要 | Background: Cytochrome c (cyt c) is well known for its role in mitochondrial electron transport. The redox state of cyt c has recently been linked to apoptosis. In the present study, we investigated and compared the kinetics of cyt c reduction by various thiol antioxidants. Methods: All kinetic experiments were performed by measuring spectrophotometrically the changes in absorbance at 550 nm for 2 min at 25oC in a reaction buffer (50 mM Tris HCl, pH 7.4) containing cyt c (5 μM) and thiols (100 μM). Electrostatic effects on the rate of reduction of cyt c were determined by varying the ionic strength of the reaction buffer. The kinetic data were treated by applying a pseudo fi rst-order approximation. Results: The results show that, among all thiols studied, cysteine reduces cyt c at the highest rate. The second-order rate constant is on the order of 102 M-1s-1 for cellular thiol reductants, GSH and cysteine. Most thiols of therapeutic importance exhibit extremely low reduction rates. Moreover, the rate of cyt c reduction was found to correlate negatively with the pKa of the SH group. This study further demonstrates that a complex electrostatic interaction may occur between cyt c and thiols. Conclusions: Given the high abundance of GSH in cells, our kinetic data suggest that GSH may out-compete other reductants for cyt c; and is therefore an important mediator of the cellular redox state of cyt c. |
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