Superoxide dismutases

Two different superoxide dismutases (SODs) are found in mammalian tissues a Cu/Zn-containing enzyme which is found in the cytoplasm of most cells, and a further Mn-containing enzyme present within the mitochondrial compartment [1], Both enzymes catalyse the same reaction  

The Zn2+ is not thought to function in the catalytic process directly, but more probably serves to stabilize the enzyme other cations such as Co2+, Hg2+ and Cd2+ have been shown to confer greater stability on the enzyme than the native Zn2+. The complete amino-acid structure of several Cu/Zn SODs has been determined and is very similar in enzymes from different sources. Detailed three-dimensional structural studies have also been undertaken [2], 

The cytosolic compartment in mammalian cells is protected from oxidative damage caused by H2O2, by catalase and by the selenoenzyme glutathione peroxidase (GSHPx) GSHPx is also present in the mitochondria of all mammalian cells. 

Catalase is an enzyme that is present in most aerobic cells of a wide variety of origins, and is located in most plant and animal cells in the single membrane-bounded organelles known as peroxisomes [1]. In human tissues there is a very high concentration of the enzyme in liver and erythrocytes, and there is relatively much less in brain, heart and skeletal muscle [3], The general reaction catalysed by the enzyme is  

The question as to the non-peroxisomal existence of catalase in animal cells is a vexing one it may be that the catalase that can be detected in the soluble fraction of mammalian cell homogenates has been released from the organelles by the mechanical friction of homogenization however, there is some evidence that suggests that some non-peroxisomal catalase exists in the liver. 

Clinical Consequences. 2e Robert Crichton Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-49223-X (Hardback) 0-470-84579-1 (Electronic) 

A coordination number of 6 is that most frequently found for both Fe(II) and Fe(III), giving octahedral stereochemistry although four- (tetrahedral) and, 

The unique suitability of iron comes from the extreme variability of the Fe2+/Fe3+ redox potential, which can be fine tuned by well-chosen ligands, so that iron sites can encompass almost the entire biologically significant range of redox potentials, from about —0.5 V to about +0.6 V. 

Ferrous or cuprous state does not give Fenton reaction 

The ferrous or the cuprous state give Fenton reaction 

As discussed above, some SODs are cambialistic and they are equally active with either Fe or Mn bound at their catalytic centers [92]. On the other hand, the authentic Mn-depending SOD from E. coli can only be active when Mn is bound. However, this enzyme can also bind Fe and thus be rendered inactive. This is puzzling because the closely related E. coli Fe and Mn SODs have very similar first coordination spheres (Fig. 11.11) with three histidine and one aspartate side chain and a H2O/OH (depending on the redox state) as ligands [98-102]. The coordination is almost exactly trigonal bipyramidal. The relationship between metal binding and activity seems to be controlled by outer-sphere ligands to the solvent 

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Klapper, I., Hagstrom, R., Fine, R., Sharp, K., Honig, B. Focusing of electric fields in the active site of cu,zn superoxide dismutase. Proteins Struct. Pune. Genet. 1 (1986) 47-79. 

Klapper 1, R Hagstrom, RFine, K Sharp and B Honig 1986. Focusing of Electric Fields in tire Actir e Sit of CuZn Superoxide Dismutase Effects of Ionic Strength and Amino-Acid Substitution. Proteins Structure, Function and Genetics 1 47-59. 

Super milling dyes Supermumetal Supernovas Superoxide dismutase... 

Erythrocuprein, which contains about 60 wt % of the erythrocyte copper, hepatocuprein, and cerebrocuprein act as superoxide dismutases. Each contains two atoms of copper per molecule, having mol wt ca 34,000. The superoxide ion, O", and peroxide, two main toxic by-products of... 

Copper is one of the twenty-seven elements known to be essential to humans (69—72) (see Mineral nutrients). The daily recommended requirement for humans is 2.5—5.0 mg (73). Copper is probably second only to iron as an oxidation catalyst and oxygen carrier in humans (74). It is present in many proteins, such as hemocyanin [9013-32-3] galactose oxidase [9028-79-9] ceruloplasmin [9031 -37-2] dopamine -hydroxylase, monoamine oxidase [9001-66-5] superoxide dismutase [9054-89-17, and phenolase (75,76). Copper aids in photosynthesis and other oxidative processes in plants. 

Superoxide dismutase has been approved by the FDA for preventing reperfusion injury or damage to donor organ tissue (178). This enzyme is prepared by recombinant DNA technology and marketed by Bristol-Myers and Pharmacia-Chiron. 

Two classes of antioxidants are known the low-molecular weight compounds (tocopherols, ascorbate, -carotene, glutathione, uric acid and etc.) and the proteins (albumin, transferrin, caeruloplasmin, ferritin, etc.) including antioxidant enzymes (e.g. superoxide dismutase, catalase, glutathione peroxidase). 

Copper-zinc-superoxide dismutase (from blood cell haemolysis) [9054-89-1J Mr 32,000... 

CL Eisher, J-L Chen, J Li, D Bashford, L Noodleman. Density-functional and electrostatic calculations for a model of a manganese superoxide dismutase active site in aqueous solution. J Phys Chem 100 13498-13505, 1996. 

J Shen, CF Wong, S Subramaniam, TA Albright, JA McCammon. Partial electrostatic charges for the active center of Cu,Zn superoxide dismutase. J Comput Chem 11 346-350, 1990. 

Figure S.l The enzyme superoxide dismutase (SOD). SOD is a P structure comprising eight antiparallel P strands (a). In addition, SOD has two metal atoms, Cu and Zn (yellow circles), that participate in the catalytic action conversion of a superoxide radical to hydrogen peroxide and oxygen. The eight p strands are arranged around the surface of a barrel, which is viewed along the barrel axis in (b) and perpendicular to this axis in (c). [(a) Adapted from J.S. Richardson. The stmcture of SOD was determined in the laboratory of J.S. and D.R. Richardson, Duke University.)...

McLachlan, A.D. Repeated folding pattern in copper-zinc superoxide dismutase. Nature 285 267-268, 1980. 

Richardson, J.S., et al. Similarity of three-dimensional stmcture between the immunoglobulin domain and the copper, zinc superoxide dismutase subunit. 

Tainer, J.A., et al. Determination and analysis of the 2 A structure of copper, zinc superoxide dismutase. 

When H2O2 is a necessary component of a luminescence system, it can be removed by catalase. If a luminescence system involves superoxide anion, the light emission can be quenched by destroying O2 with superoxide dismutase (SOD). The ATP cofactor usually present in the fresh extracts of the fireflies and the millipede Luminodesmus can be used up by their spontaneous luminescence reactions, eventually resulting in dark (nonluminous) extracts containing a luciferase or photoprotein. The process is, however, accompanied by a corresponding loss in the amount of luciferin or photoprotein. The use of ATPase and the elimination of Mg2+ in the extract may prevent such a loss. 

McCord, J. M., and Fridovich, I. (1969). Superoxide dismutase an enzymic function for erythrocuprein (hemocuprein)./. Biol. Chem. 244 6049-6055. 

Nakano, M. (1990). Assay for superoxide dismutase based on chemiluminescence of luciferin analog. Method. Enzymol. 186 227-232. 

Shimomura, O. (1992). The role of superoxide dismutase in regulating the light emission of luminescent fungi. J. Exp. Botany 43 1519-1525. 

Suzuki, N., etal. (1991). Reaction rates for the chemiluminescence of Cypridina luciferin analogs with superoxide a quenching experiment with superoxide dismutase. Agric. Biol. Chem. 55 157-160. 

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