Spectroscopy, superoxide dismutases

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. 

BH4 = Tetrahydrobiopterin CAM = Cytotoxic activated macrophage cNOS = Constitutive nitric oxide synthase CPR = Cytochrome P450 reductase EDRF = Endothelial-derived relaxation factor EPR = Electron paramagnetic resonance spectroscopy IL-1 = Interleukin-1 iNOS = Inducible nitric oxide synthase EPS = Lipopolysaccharide, or endotoxin NMMA = ISp-monomethyl-L-arginine NOS = Nitric oxide synthase ROS = Reactive oxygen species SOD = Superoxide dismutase TNF = Tumor necrosis factor. 

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. 

Both charge isomers have a relative molecular mass of32,000 daltons. The isomerism is attributed to the different isoelectric points of the proteins No differences were found in metal content, antigenicity, electron paramagnetic resonance and electron absorption spectroscopy Holo- and apo-superoxide dismutase, which have electro-... 

EPR-spectroscopy of the steady state level of CUjZn superoxide dismutase is a less perturbative method. It was applied to crude haemolysates. If SOD is added in a concentration of about 10 M, a superoxide flux of 2.0x10 Mol x sec was detected Increasing the PO2 caused a saturation of O2 -production. The autoxida-... 

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