Copper-zinc superoxide dismutase measurement

The simplest direct assay was described by Marklund (1976). Superoxide was generated from its potassium salt at alkaline pH where its stability increases. The decay at 250 nm in the presence and absence of superoxide dismutase is measured in a standard spectrophotometer. The assay is carried out in such a way that the rate of a decay in the presence of the enzyme is within the time response of the apparatus (Fig. 1). One unit of activity is arbitrarily taken as the enzyme activity that results in the dismutation of O2 at a rate of 0. lsec . This rate of dismutation corresponds to 5.5 ng bovine copper/zinc superoxide dismutase and to 64.5 ng bovine manganese superoxide dismutase under the conditions described by Marklund (1976). The rate constants calculated for both enzymes were... 

The structure and enzyme kinetics of bovine erythrocyte superoxide dismutase are reviewed. The protein has a novel imidazolate-bridged copper(II)-zinc(II) catalytic center in each of two identical subunits. Since a C /Cu1 redox couple is responsible for the dismutase activity of the enzyme, the role of zinc is of interest. Both 220-MHz NMR measurements of the exchangeable histidine protons and chemical modifications using diethylpyrocarbonate demonstrate that zinc alone can fold the protein chain in the region of the active site into a conformation resembling that of the native enzyme. Other possible roles for zinc are discussed. Synthetic, magnetic, and structural studies of soluble, imidazolate-bridged copper complexes of relevance to the 4 Cu(II) form of the enzyme have been made. 

When rats are administered with bacoside A (10 mg/kg), levels of glutathimie, vitamin C, vitamin E, and vitamin A were reduced. The activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were also assayed. Copper, iron, zinc, and selenium levels in brain and serum ceruloplasntin activity were also measured. Administration of bacoside A improved the antioxidant status and maintained the levels of trace elements [16]. 

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