Spectroscopy, superoxide dismutases copper

Palivan, C.G., Palivan, H. and Goodman, BA. (1994) Characterisation by EPR spectroscopy of the co-ordination environment of copper in superoxide dismutase from horseradish (Armoracia rusticana Gaertn.). Proc. R. Soc. Edin., 102B, 273-277. 

CD spectroscopy has also provided valuable insight into the chemical stability and chemical denaturation of proteins. A recent study by Rumfeldt etal. examines the guanidinium-chloride induced denaturation of mutant copper-zinc superoxide dismutases (SODs). These mutant forms of the Cu, Zn-SOD enzyme are associated with toxic protein aggregation responsible for the pathology of amyotrophic lateral sclerosis. In this study, CD spectroscopy was used in conjunction with tryptophan fluorescence, enzyme activity, and sedimentation experiments to study the mechanism by which the mutated enzyme undergoes chemical denaturation. The authors found that the mutations in the enzyme structure increased the susceptibihty of the enzyme to form partially unfolded destabilized monomers, rather than the stable metaUated monomer intermediate or native metallated dimer. 

The reactivity of native erythrocuprein was higher compared to the superoxide dismutase activity shown in Table 12. Of utmost importance was the observation that the model chelates and CUSO4 were virtually inactive compared to the native enzyme. The difference was 4 orders of magnitude which implies a much higher specificity for this enzymic reaction of the cupreins. The powerful reactivity of erythrocuprein is further demonstrated by the fact that the apoprotein displayed a detectable enzymic activity due to traces of copper which were undetectable by atomic absorption measurements or EPR spectroscopy. No such difference between apoprotein and the boiled native enzyme was observed using the superoxide dismutase assay. 

The kinetics of formation of the intermediate complex between catalase and HgOa have been re-examined, and reports of pulse radiolysis experiments with superoxide dismutase and its manganese-containing form have appeared. Bovine superoxide dismutase is known to contain two Cu and two Zn atoms per molecule and it has been shown that the copper site, which is directly involved in the catalytic activity, comprises three nitrogens and a water molecule bound to the metal in a field with less than axial symmetry. Less is known of the zinc site but it has recently been shown, by e.p.r. spectroscopy with the cobalt-copper form of the enzyme, that the... 

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