Inactivation of Copper,Zinc superoxide dismutase by H2O2 : Mechanism of protection |
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| Affiliation: | 1. Department of Life Science, Sogang University, 35, Baekbeom-ro, Mapo-gu, Seoul 121-742, Republic of Korea;2. Division of Allergy and Respiratory Medicine, Soonchunhyang University Bucheon Hospital, 1174, Jung-dong, Wonmi-gu, Gyeonggi-do 420-020, Republic of Korea;3. Department of Genetic Epidemiology, SNP Genetics, Inc., 35, Baekbeom-ro, Mapo-gu, Seoul 121-742, Republic of Korea;4. Division of Allergy and Respiratory Medicine, Soonchunhyang University Seoul Hospital, 59, Daesagwan-ro, Yongsan-gu, Seoul 140-887, Republic of Korea;5. Division of Allergy and Respiratory Medicine, Soonchunhyang University Cheonan Hospital, 23-20, Byeongmyeong-dong, Dongnam-gu, Cheonan, Chungcheongnam-do 330-721, Republic of Korea;6. Division of Allergy and Respiratory Medicine, Soonchunhyang University Gumi Hospital, 250, Gongdan-dong, Gumi, Kyungsangbook-do 730-706, Republic of Korea |
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| Abstract: | Cu,Zn SOD is known to be inactivated by HO2− and to be protected against that inactivation by a number of small molecules including formate, imidazole, and urate. This inactivation has been shown to be due to oxidation of a ligand field histidine residue by a bound oxidant formed by reaction of the active site Cu(II) with HO2−. We now report that protective actions of both formate and NADH increase as the pH was raised in the range 8.0–9.5. This is taken to indicate increased accessibility of the Cu site with rising pH and/or increased reactivity of the bound oxidant toward exogeneous substrates at high pH. Formate appears to act as a sacrificial substrate that protects by competing with the endogenous histidine residue for reaction with the bound oxidant, or that repairs the damage by reducing the histidyl radical intermediate. The same is likely also true of NADH. |
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