Kinetics and Mechanism of Reduction of Coordinated Superoxide with Glutathione and Cysteine

• Main Authors: Hsin-Yi Wang, 王馨怡
• Other Authors: Shao-Yung Lee
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/bw2gu6

碩士 === 義守大學 === 化學工程學系暨生物技術與化學工程研究所 === 104 === Superoxide anion would be produced in the process of human respiratory or metabolic pathway. Free superoxide ions are reactive and not stable in aqueous solution. However, the reactivity of the superoxide anion bonded dinuclear metal complexes are studied extensively in aqueous solution. Glutathione plays key roles in biological systems and serves many cellular functions such as the maintenance of intracellular redox states, detoxification, and metabolism. The ratio of GSH to its oxidized form GSSG in cells is a predictor of fatal diseases like Diabetes mellitus, Alzheimer''s, Parkinson''s disease, Cancer or AIDS. In this work, the kinetics and mechanism of the oxidation of glutathione by -superoxo complex [(en)(dien)Co(O2)Co(en)(dien)]5+ was studied. The kinetics was studied in pseudo-first order kinetic condition. The reaction is first-order dependence of both -superoxo complex and glutathione. The rate law is therefore described as follow : rate = k[(en)(dien)Co(O2)Co(en)(dien)]5+[GSH] The second order rate constant k of the oxidation of glutathione with [(en)(dien)Co(O2)Co(en)(dien)]5+ at 25 ℃ is determined as 9.57 M-1s-1. The kinetics and mechanism of the oxidation of cysteine with [(en)(dien)Co(O2)Co(en)(dien)]5+ was also studied since the active site of glutathione is the sulfhydryl (-SH) of cysteine. The reaction is also first-order dependence of both -superoxo complex and cysteine, The second order rate constant k at 25 ℃ is determined as 11.03 M-1s-1. The dependence of hydrogen ion, temperature and activation enthalpy, activation entropy were also examined.