Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.15.1.1 (superoxide dismutase)
 58,858 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Superoxide dismutase has been isolated and characterised from the extreme thermophile Thermus aquaticus. The pure enzyme is a reddish-purple manganese-containing protein with a molecular weight of approximately 80000 +/- 5000. Combination of gel electrophoresis in dodecylsulphate and amino acid analysis shows that it is composed of four identical subunit polypeptide chains consisting of approximately 186 amino acids. The tetrameric protein contains two atoms of manganese. A stable manganese-free apoprotein has been prepared by treatment with EDTA in 8 M urea at acidic pH. The apoprotein regains the tetrameric structure in the absence of manganese but is inactive. Reconstitution of active Mn-enzyme was achieved byaddition of Mm2+ apoprotein in 8 M urea at acid pH. Reconstitution was monitored by absorption spectroscopy, manganese analysis and regain of activity and by these criteria the reconstituted enyzme with two atoms Mn per mole is indistinguishable from the native enzyme. The enhanced stability of the thermophile apoenzyme and Mn-enzyme is of advantage for studies of the structure and mechanism of action of superoxide dismutase. The N-terminal amino acid sequence to the 40th residue of the submit was determined by automated Edman degradation. The sequence has a close resemblance to that of the dimeric Mn-enzyme from another thermophile, Bacillus stearothermophilus.
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PMID:Superoxide dismutase from Thermus aquaticus. Isolation and characterisation of manganese and apo enzymes. 1 28

The air oxidation of procarbazine in the presence of Ti(IV) was examined as a model system for the effects titanium has on oxidative processes and intermediates involving molecular oxygen. It was found that Ti(IV) inhibited oxidation when the substrate, procarbazine, was coordinated to titanium. This inhibition was most prominent (reduction of overall rate constant by a factor of 10(2)) in its interference with Cu(II) catalyzed oxidation of the substrate whole oxidation by the neutral species O2 was only slightly inhibited (factor of 2). However, when Mn(II) was used to catalyze the oxidation of procarbazine by air, titanium enhanced the catalytic effect of Mn(II) by a factor of 10(2). This enhancement was found to be due to Ti(IV) catalysis of the air oxidation of Mn(II), and the effect was found to be inhibited by catalase but not superoxide dismutase or peroxidase. These results are discussed in terms of a Ti(IV) ability to activate molecular oxygen and its ability to form oxygen free-radical complexes.
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PMID:Oxidation of procarbazine in the presence of Ti(IV). 1 28

Partially purified soluble rat liver guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] was activated by superoxide dismutase (superoxide: superoxide oxidoreductase, EC 1.15.1.1). This activation was prevented with KCN or glutathione, inhibitors of superoxide dismutase. Guanylate cyclase preparations formed superoxide ion. Activation by superoxide dismutase was further enhanced by the addition of nitrate reductase. Although guanylate cyclase activity was much greater with Mn2+ than with Mg2+ as sole cation cofactor, activation with superoxide dismutase was not observed when Mn2+ was included in incubations. Catalase also decreased the activation induced with superoxide dismutase. Thus, activation required the formation of both superoxide ion and H2O2 in incubations. Activation of guanylate cyclase could not be achieved by the addition of H2O2 alone. Scavengers of hydroxyl radicals prevented the activation. It is proposed that superoxide ion and hydrogen peroxide can lead to the formation of hydroxyl radicals that activate guanylate cyclase. This mechanism of activation can explain numerous observations of altered guanylate cyclase activity and cyclic GMP accumulation in tissues with oxidizing and reducing agents. This mechanism will also permit physiological regulation of guanylate cyclase and cyclic GMP formation when there is altered redox or free radical formation in tissues in response to hormones, other agents, and processes.
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PMID:Activation of guanylate cyclase by superoxide dismutase and hydroxyl radical: a physiological regulator of guanosine 3',5'-monophosphate formation. 2 77

Superoxide dismutase from Mycobacterium species, strain Takeo, has been purified to homogeneity as judged by disc gel electrophoresis and ultracentrifugation. The enzyme was found to have a molecular weight of approximately 61 500 by sedimentation equilibrium and to contain manganese by atomic absorption and electron spin resonance spectra. The amino acid composition was also determined. The enzyme was considerably stable to the treatment with sodium dodecyl sulfate; unless incubating at 80 degrees C for 2 min, it was not completely dissociated into the subunits. The molecular weight of the subunit was found to be approximately 21 000. Antibodies against the superoxide dismutase were produced by immunization of rabbits with the enzyme, and the gamma-globulin fraction was purified. Superoxide dismutase preparations obtained from various species of mycobacteria and nocardia cross-reacted to different degrees with these antibodies on the Ouchterlony double diffusion plates. Comparative immunological studies indicated that strain Takeo might be most closely related to Myobacterium smegmatis among species of mycobacteria and nocardia tested. The antibodies against superoxide dismutase may be used as a valuable tool for the classification of mycobacteria.
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PMID:Superoxide dismutase from Mycobacterium species, strain Takeo. 5 47

Previous studies have demonstrated a 50% increase in pulmonary superoxide dismutase (SOD) activity in oxygen-adapted rats and have suggested that SOD plays a significant role in the development of "tolerance". To further study these events, the cuprozinc SOD was purified from rat liver and found to be similar to previously purified cuprozinc superoxide dismutases. A rabbit antisera to rat cuprozinc SOD was produced and used to perform antibody titrations of SOD in the lungs of rats exposed to 85% O2 for 5 days. The absolute amount of cuprozinc SOD increased 41% by antibody titration which accounted for most, if not all, of the 48% increase demonstrated in total SOD activity. Spectrophotometric assays at pH 7.8 and 10.0 of pure rat cuprozinc SOD and crude lung homogenates suggest that there is also a manganese SOD present, but the role of that SOD in the development of oxygen tolerance has not been established.
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PMID:Oxygen-induced changes in pulmonary superoxide dismutase assayed by antibody titrations. 13 5

Analysis of the metal content, CD and EPR spectra, and reaction with H(2)O(2) and ferrocyanide have been carried out on E. coli superoxide dismutase, which contains manganese as the metal prosthetic group. The results obtained indicate that the metal is present in the enzyme as a high spin Mn(III) complex of highly distorted octahedral symmetry, in the ratio of approximately 1 atom of manganese per enzyme dimer.
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PMID:CD spectra and redox reactions of superoxide dismutase from Escherichia coli B: evidence for a Mn(III) enzyme. 16 58

(1) Aerobic incubation of heart muscle submitochondrial particles in phosphate buffer after treatment with NADH causes a progressive and substantial inhibition of the NADH oxidation system. Succinate oxidation remains almost unaffected by NADH treatment. (2) The loss of NADH oxidase activity is due to an inhibition of the respiratory chain-linked NADH dehydrogenase. This inhibition of the enzyme is very similar to that caused by combination of the organic mercurial mersalyl with NADH dehydrogenase. (3) The inhibition of NADH oxidation is largely prevented by compounds that are known to react with superoxide ions (02-.), including superoxide dismutase, cytochrome c, tiron and Mn2+. EDTA also has a protective effect, but a number of other metal chelating agents, and several proteins, including catalase, are without effect. (4) It is concluded that the inhibition of NADH oxidation of NADH oxidation by superoxide ions or by mersalyl is reversible and is therefore not due to the loss of oxidoreduction components from the respiratory chain or to an irreversible change in protein conformation. (6) The function of mitochondrial superxide dismutase is discussed in relation to the key role of NADH dehydrogenase in energy-conserving reactions and the formation of hydrogen peroxide during mitochondrial oxidations.
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PMID:A protective function of superoxide dismutase during respiratory chain activity. 16 98

Human platelets contain the cuprozinc (cytoplasmic) and manganese (mitochondrial) forms of superoxide dismutase. Nevertheless, superoxide radicals were detectable in the surrounding medium of metabolically viable platelet suspensions by using two assay systems: cytochrome c and nitroblue tetrazolium. The quantity of superoxide generated by platelets (5 X 10(5) superoxide radicals/platelet per 10 min) was constant and did not increase after aggregation by agents such as collagen and thrombin. The superoxide-generating system was present in the supernate of both aggregated and resting platelets and therefore was not platelet-bound. Platelet superoxide production was unaffected by prior ingestion of aspirin, indicating that the prostaglandin and thromboxane pathways were not involved. Both resting and aggregated platelets exhibited a reductive capacity toward cytochrome c and nitroblue tetrazolium which was unrelated to superoxide production. Furthermore, the aggregation process always resulted in a marked increase in this reduction. The nonsuperoxide reduction associated with aggregation was found to be membrane bound and to decrease with an apparent first order reaction rate (k1 = 0.067 min-1). In addition, accumulative, time-dependent nonsuperoxide-related cytochrome c reduction was also detected. Since there is no superoxide dismutase in plasma, the presence of superoxide radicals in the surrounding medium of platelets may have in vitro significance for platelet and leukocyte concentration and storage and in vivo significance for hemostasis, coagulation, and thrombosis. The nonsuperoxide-related reducing activities may represent a biochemical basis for platelet-blood vessel interactions, with particular reference to blood vessel integrity.
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PMID:Superoxide production and reducing activity in human platelets. 18 22

1. Dihydroxyfumarate slowly autoxidizes at pH6. This reaction is inhibited by superoxide dismutase but not by EDTA. Mn2+ catalyses dihydroxyfumarate oxidation by reacting with O2 leads to to form Mn3+, which seems to oxidize dihydrofumarate rapidly. Cu2+ also catalyses dihydroxyfumarate oxidation, but by a mechanism that does not involve O2 leads to. 2. Peroxidase catalyses oxidation of dihydroxyfumarate at pH6; addition of H2O2 does not increase the rate. Experiments with superoxide dismutase and catalase suggest that there are two types of oxidation taking place: an enzymic, H2O2-dependent oxidation of dihydroxyfumarate by peroxidase, and a non-enzymic reaction involving oxidation of dihydroxyfumarate by O2 leads to. The latter accounts for most of the observed oxidation of dihydroxyfumarate. 3. During dihydroxyfumarate oxidation, most peroxidase is present as compound III, and the enzymic oxidation may be limited by the low rate of breakdown of this compound. 4. Addition of p-coumaric acid to the peroxidase/dihydroxyfumarate system increases the rate of dihydroxyfumarate oxidation, which is now stimulated by addition of H2O2, and is more sensitive to inhibition by catalase but less sensitive to superoxide dismutase. Compound III is decomposed in the presence of p-coumaric acid. p-Hydroxybenzoate has similar, but much smaller, effects on dihydroxyfumarate oxidation. However, salicylate affects neither the rate nor the mechanism of dihydroxyfumarate oxidation. 5. p-Hydroxybenzoate, salicylate and p-coumarate are hydroxylated by the peroxidase/dihydroxyfumarate system. Experiments using scavengers of hydroxyl radicals shown that OH is required. Ability to increase dihydroxyfumarate oxidation is not necessary for hydroxylation to occur.
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PMID:Generation of hydrogen peroxide, superoxide and hydroxyl radicals during the oxidation of dihydroxyfumaric acid by peroxidase. 19 74

Streptococcus faecalis contains a single superoxide dismutase that has been purified to homogeneity with a 55% yield. This enzyme has a molecular weight of 45,000 and is composed of two subunits of equal size. It contains 1.3 atoms of manganese per molecule. Its amino acid composition was determined and is compared with that for the superoxide dismutases from Escherichia coli, Streptococcus mutans, and Mycobacterium lepraemurium. When used as an antigen in rabbits, the S. faecalis enzyme elicited the formation of a precipitating and inhibiting antibody. This antibody cross-reacted with the superoxide dismutase present in another strain of S. faecalis, but neither inhibited nor precipitated the superoxide dismutases in a wide range of other bacteria, including several other streptococci, such as S. pyogenes, S. pneumoniae, and S. lactis. The inhibiting antibody was used to suppress the superoxide dismutase activity present in cell extracts of S. faecalis and thus allow the demonstration that 17% of the total oxygen consumption by such extracts, in the presence of reduced nicotinamide adenine dinucleotide, was associated with the production of O(2) (-). A variety of bacterial species were surveyed for their content of superoxide dismutases. The iron-containing enzyme was distinguished from the manganese-containing enzyme through the use of H(2)O(2), which inactivates the former more readily than the latter. Some of the bacteria appeared to contain only the iron enzyme, others only the manganese enzyme, and still others both. Indeed, some had multiple, electrophoretically distinct superoxide dismutases in both categories. There was no discernible absolute relationship between the types of superoxide dismutases in a particular organism and their Gram-stain reaction.
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PMID:Superoxide dismutase and oxygen metabolism in Streptococcus faecalis and comparisons with other organisms. 20 36


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