Superoxide dismutase, anion binding

Fig. 6. Suggested changes in the coordination at tte copper (xntre upon anion binding and during the catalytic cycle of Cu—Za superoxide dismutase...

XAS has proved particularly successful in deilning the structural changes which occur upon reduction and anion binding to superoxide dismutase thus providing a unique insight into the structure-function relationships in the Cu Zn SOD. The anion-binding studies have been particularly relevant due to the close similarity of the anions such as cyanide and azide to the superoxide substrate. 

The enzyme copper, zinc superoxide dismutase (Cu,Zn-SOD, EC 1.15.1.1) catalyzes the disproportionation of superoxide anion to dioxygen and hydrogen peroxide (equations 1 and 2). Crystallographic data can be found in References 41-46. This antioxidant enzyme is present in the cytosol and mitochondrial intermembrane space of eukaryotic cells and in the periplasmic space of bacterial cells as a homodimer of 32 kDa. Each monomer binds one copper and one zinc ion. The reaction mechanism involves the... 

Cass, A. E. G., Hill, H. A. O. Anion binding to copper(I) superoxide dismutase A high resolution H nuclear magnetic resonance spectroscopic study. In Chemical and Biochemical Aspects of Superoxide and Superoxide Dismutase (Bannister, J. V., Hill, H. A, O., eds.). New York-Amsterdam-Oxford, Elsevier/North-Holland, 1980, pp. 290-298... 

Sette, M., Paci, M., Desideri, A. and Rotillo, G. (1992) Formate as an NMR probe of anion binding to copper-zinc and copper-cobalt bovine erythrocyte superoxide dismutase. Biochemistry, 31, 2410-2415. 

Some of the copper enzymes that have not been associated with a specific pathological defect include cytochrome c oxidase, the terminal enzyme in the mitochondrial electron transport system superoxide dismutase, the enzyme that catalyzes the dismutation of toxic superoxide anions dopamine-g-hydroxylase, the enzyme that catalyzes the conversion of dopamine to norepinephrine and uricase, the enzyme that catalyzes the oxidation of uric acid. Careful analysis of the pathological defects that accompany copper deficiency will probably lead to association of some of these enz3ones with specific pathological defects. However, some of these enzymes may bind copper very tenaciously or have a slow turnover... 

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