Superoxide dismutase EC

Superoxide dismutase (SOD) scavenges superoxide radicals, Oj according to the reaction  

The H2O2 formed may be reduced by catalase, peroxidase or suitable reducing agents. SOD has been identified in many animal and bacterial cells its biological function is to protect tissue against oxygen free radicals in anaerobic systems (reviewed by Farkye, 1992). 

isolated from bovine erythrocytes, is a blue-green protein due to the presence of copper, removal of which by treatment with EDTA results in loss of activity, which is restored by adding Cu it also contains Zn , which does not appear to be at the active site. The enzyme, which is very stable in 9 M urea at neutral pH, consists of two identical subunits of molecular weight 16kDa held together by one or more disulphide bonds. The amino acid sequence has been established. 

Milk contains trace amounts of SOD which has been isolated and characterized it appears to be identical to the bovine erythrocyte enzyme. SOD inhibits lipid oxidation in model systems. The level of SOD in milk parallels that of XO (but at a lower level), suggesting that SOD may be excreted in milk in an attempt to offset the pro-oxidant effect of XO. However, the level of SOD in milk is probably insufficient to explain observed differences in the oxidative stability of milk. The possibility of using exogenous SOD to retard or inhibit lipid oxidation in dairy products has been considered. 

SOD is more heat stable in milk than in purified preparations in milk it is stable at 71°C for 30 min but loses activity rapidly at even slightly higher temperatures. Slight variations in pasteurization temperature are therefore critical to the survival of SOD in heated milk products and may contribute to variations in the stability of milk to oxidative rancidity. 

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IV. Superoxide dismutase (EC 1.15.1.1) Within a cell the superoxide dismutases (SODs) constitute the first line of defense against ROS. Superoxide radical (02) is produced where an electron transport chain is present, as in mitochondria and chloroplasts, but 02 activation may occur in other subcellular locations such as glyoxysomes, peroxisomes, apoplast and the cytosol. Thus SODs are present in all these cellular locations, converting superoxide into hydrogen peroxide and water (i.e. copper/zinc SODs are typically found in the nuclei and cytosol of eukaryotic cells). 

The imidazole-bridge dimetallic centre in copper-zinc superoxide dismutase (EC 1.15.1.1) was a novel structural feature that had not previously been encountered in coordination chemistry [151], The Cu(II) ion is co-ordinated by four histidine side chains, His44, His46, His 118 and His61, and there is evidence for a fifth axial water ligand. 

The three-dimensional structure of human extracellular superoxide dismutase (EC-SOD) is unknown. Studies of structure-function relationships have been severely limited by its poor production in mammalian cell lines and failure to be expressed in prokaryotic and yeast systems. In contrast, extra- and intracellular Cu- and Zn-containing superoxide dismutases (CuZn-SOD) are expressed very well in E. coli and yeast. CuZn-SOD is homologous to a large interior fragment of EC-SOD, but lacks its extra N-terminal and C-terminal domains. Fusions of either the N-terminal domain of EC-SOD or both the N- and C-terminal domains of EC-SOD to CuZn-SOD resulted in a domain-swapped enzyme that expressed well and whose characteristics resemble EC-SOD (Stenlund and Tibell, 1999). 

The enzyme superoxide dismutase (EC 1.15.1.1) is unique in that it has three isozymes whose only similarity is that they catalyze the same reaction - 2O2 + H2O2 + O2. There are not only different forms... 

Here two isozymes of superoxide dismutase (EC 1.15.1.1) from Scots pine (Pinus silvestris L.) needles was purified and their sub-cellular location was determined. 

Treatment of rats with melatonin and vitamins E plus C significantly (P < 0.05) reduced the chlor-pyrifos-ethyl-induced increase of thiobarbituric acid-reactive substance in erythrocytes, and overcame the inhibitory effect of chlorpyrifos-ethyl on superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6), but not on antioxidant defence potential (Gultekin et al. 2001). Melatonin treatment significantly P < 0.05) increased only glutathione peroxidase (EC 1.1.1.9) activity, irrespective of the effect of chlorpyrifos-ethyl. 

Captopril succeeded in suppressing oedema evolution in hind paws of Freund s arthritic Wistar rats, during all phases of the disease (Agha and Mansour 2000). During the chronic phase of inflammation, in both Freund s arthritic and mixed-type hypersensitive rats, captopril reduced the elevated serum and exudate (local) leukotriene B4 and IL-6 levels. The effect of leukotriene B4 was more pronounced in the exudate and tended to be dose-related. The antiarthritic effect of captopril was also accompanied by augmentation of serum level of protein thiols, with reduction or normalisation of elevated systemic and/or local levels of lipid peroxide, superoxide dismutase (EC 1.15.1.1) and glutathione. 

In 14-day bleomycin (1.5 mg in sterile sahne i.p. daily)-treated rats (205 6 g body weight) type 2 alveolar epithelial cells were swollen with enlarged lamellar inclusion bodies (Karam et al. 1998). Biochemical study of freshly isolated cells displayed a significant decrease of lactate dehydrogenase (EC 1.1.1.27) released by these cells when isolated from 14-day-treated rats as compared with 7-day. By contrast, bleomycin induced an increase in superoxide dismutase (EC 1.15.1.1) and glutathione peroxidase (EC 1.11.1.9) activities. Cell content of glutathione was decreased and y-glutamyl transpeptidase activity was markedly increased. 

While the number of macrophages recoverable from cultures of rabbit alveolar macrophages exposed to hyperoxia for 72 h was decreased compared with that in normal control cultures exposed to normoxia for similar durations, addition of di-methylthiourea or catalase (EC 1.11.1.6), but not superoxide dismutase (EC 1.15.1.1), increased the number of macrophages recoverable from cultures exposed to hyperoxia (Harada et al. 1983). Alveolar macrophages exposed to hyperoxia in the presence of dimethylthiourea or catdase, but not superoxide dismutase, did not develop ultrastructural abnormalities as vacuolisation and cytoplasmic and nuclear degeneration. 

The enhanced production of superoxide ion (02 ) and peroxynitrite (ONOO") by bloodstream neutrophils and superoxide ion by monocytes from rheumatoid arthritis patents was registered by luminol- or lucigenin-enhanced chemiluminescent measurement (Ostrakhovitch and Afanas ev 2001). Superoxide dismutase (EC 1.15.1.1) and rutin were the most efficient suppressors of oxygen radical overproduction by rheumatoid arthritis neutrophils, while mannitol and desferrioxamine were ineffective. 

Erythrocyte Cu /Zn superoxide dismutase (EC 1.15.1.1) activity was significantly higher in a group of 34 underground coal miners from Lorraine than in a group of 30 surface workers (Perrin-Nadif et al. 1996). 

Superoxide anion radicals (02 ) generated in alloxan diabetic rat brain tissue extracts incubated for 10 min at 25 °C with varying concentrations of xanthine (0.05,0.1,0.15, and 0.2 mM) plus xanthine oxidase (0.1. 0.2, 0.3, and 0.6 U/ml), caused a decrease in the cytosolic creatine kinase (EC 2.7.3.2) activities by 29, 50, 72, and 79 %, respectively (Genet et al. 2000). The addition of 80 pg/ml of superoxide dismutase (EC 1.15.1.1) reversed the depressed creatine kinase activities almost to control values. Hydrogen peroxide (0.001,0.01,0.1, and 1 mM) decreased the cytosolic creatine kinase activities by 5, 11, 20, and 40%, respectively. This decrease in creatine kinase activities was reversed significantly to control values when 10 p,g/ml of catalase (EC 1.11.1.6) was added to the reaction mixture during the incubation. 

Superoxide dismutase (EC 1.15.1.1) activity was found to be very high in young immature Swiss mice (Verma et al. 1991). After a subcutaneous injection of 20 /2g TSH, there was a dramatic loss (P <0.01) of SOD in the adrenal. The activity reached its lowest level at 30 min after the injection. But at 45 min after the injection, there was a significant (P <0.01) reversal of the TSH-induced SOD depletion. No significant reversal could be noted thereafter. 

CuZn-superoxide dismutase (EC 1.15.1.1) in 26-month-old rats compared with. 8-month-old animals had decreased from 30.5 1.21x10 units per g fiver tissue to 25.8 3.64 x 10 units per g liver tissue (Gomi and Matsuo 1995). 

In rabbit artery rings denuded of the endothe-hum and cultured with 0.3 p,M doxorubicin for 7 days, the contractions induced by noradrenaline, but not those induced by endothelin-1 or high lU, were strongly inhibited (Murata et al. 2001). This reaction was followed by a decrease in the induction of the ttiA-adrenoceptor without any change in the mRNA level. Inhibition of noradrenaline-induced contractions by doxorubicin was attenuated by superoxide dismutase (EC 1.15.1.1), and a,A-adrenoceptor protein expression recovered. 

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