Effect of ionic strength on the activity of bovine superoxide dismutase

Rigo, Adelio; Viglino, P.; Rotilio, G.; Tomat, Renato

doi:10.1016/0014-5793(75)81047-7

Cited by 46 publications

(17 citation statements)

References 11 publications

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“…Although it was previously observed that the presence of phosphate caused a lowering of the SOD activity of bovine Cu,Zn-SOD (Rigo et al, 1975) and that it interfered with cyanide binding (Rotilio et al, 1972), these effects were attributed to a general effect of ionic strength and not to a specific effect of phosphate (McAdam, 1977;Cudd & Fridovich, 1982). Our studies differ from those carried out previously in that they were carried out under conditions of constant ionic strength.…”

Section: Discussionmentioning

confidence: 92%

Phosphate is an inhibitor of copper-zinc superoxide dismutase

Freitas¹,

Valentine²

1984

Biochemistry

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The superoxide dismutase (SOD) activity of bovine copper-zinc superoxide dismutase (Cu,Zn-SOD) in 50 mM Hepes [4-(2-hydroxyethyl)-1- piperazineethanesulfonic acid], pH 7.4, was decreased by approximately 50% when the solution was made 10 mM in phosphate, in spite of the fact that the ionic strength of both solutions was adjusted to be equal. A similar experiment was carried out with bovine Cu,Zn-SOD chemically modified at Arg-141 with phenylglyoxal, which consequently had approximately 20% of the activity of the unmodified protein. (This activity was shown not to be due to residual unmodified protein.) Addition of 10 mM phosphate to solutions of the modified protein caused only a small decrease (less than 5%) in the SOD activity. The presence of phosphate also caused the affinity of Cu,Zn-SOD for binding azide or cyanide anions to be reduced; this effect of phosphate was also much less for the arginine-modified protein. We conclude that the inhibitory effect of phosphate on bovine Cu,Zn-SOD is due primarily to the neutralization of the positive charge on the side chain of Arg-141. The effect of increasing ionic strength on the activities of the native and arginine-modified proteins was also investigated. We found that at high concentrations of phosphate (greater than or equal to 10 mM), the SOD activities of native and arginine-modified Cu,Zn-SOD were inhibited comparably when the ionic strength was increased. This effect is presumably due to the lysine residues near the active site.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Discussionmentioning

confidence: 92%

Phosphate is an inhibitor of copper-zinc superoxide dismutase

Freitas¹,

Valentine²

1984

Biochemistry

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“…We have evidence to believe that hypoxia may also exert its effect through a mechanism that involves peroxynitrite (OONO − ) formation [38,39]. Reactive oxygen and nitrogen intermediates control the synthesis of cytokines and growth factors in several in vitro models [40].…”

Section: Discussionmentioning

confidence: 99%

Hypoxia-generated superoxide induces the development of the adhesion phenotype

Fletcher

Jiang

Diamond

et al. 2008

Free Radical Biology and Medicine

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Adhesion fibroblasts exhibit higher TGF-β1 and type I collagen expression as compared to normal peritoneal broblasts. Furthermore, exposure of normal peritoneal fibroblasts to hypoxia results in an irreversible increase in TGF-β1 and type I collagen. We postulated that the mechanism by which hypoxia induced the adhesion phenotype is through the production of superoxide either directly or through the formation of peroxynitrite. To test this hypothesis, normal peritoneal and adhesion fibroblasts were treated with superoxide dismutase (SOD), a superoxide scavenger, and xanthine/ xanthine oxidase, a superoxide-generating system, under normoxic and hypoxic conditions. Also, cells were treated with peroxynitrite. TGF-β1 and type I collagen expression was determined before and after all treatments using real-time RT/PCR. Hypoxia treatment resulted in a time-dependent increase in TGF-β1 and type I collagen mRNA levels in both normal peritoneal and adhesion fibroblasts. Similarly, treatment with xanthine oxidase, to endogenously generate superoxide, resulted in higher mRNA levels of TGF-β1 and type I collagen in both normal peritoneal and adhesion fibroblasts. In contrast, treatment with SOD, to scavenge endogenous superoxide, resulted in a decrease in TGF-β1 and type I collagen expression in adhesion fibroblasts to levels seen in normal peritoneal fibroblasts; no effect on the expression of these molecules was seen in normal peritoneal fibroblasts. Exposure to hypoxia in the presence of SOD had no effect on mRNA levels of TGF-β1 and type I collagen in either normal peritoneal or adhesion fibroblasts. Peroxynitrite treatment alone significantly induced both adhesion phenotype markers. In conclusion, hypoxia, through the production of superoxide, causes normal peritoneal fibroblasts to acquire the adhesion phenotype. Scavenging superoxide, even in the presence of hypoxia, prevented the development of the adhesion phenotype. These findings further support the central role of free radicals in the development of adhesions.

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“…Since the final concentration of the CSF in the polarographic cell was 30% v/ v, the dilution effect was taken into account in the calculation of the SOD activity. The concentration of this enzyme was calculated from the activity measurements, assuming K , = 2.3 X lo9 M-' sec-', kl being the second order kinetic rate constant of dismutation of the superoxide ion by CuSOD at 0.1 Mionic strength ( 16). The SOD content of the serum was also measured by this method.…”

Section: Methodsmentioning

confidence: 99%

Determination of Superoxide Dismutase Activity by the Polarographic Method of Catalytic Currents in the Cerebrospinal Fluid of Aging Brain and Neurologic Degenerative Diseases

Bracco

Scarpa

Rigo

et al. 1991

Experimental Biology and Medicine

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The activity of the superoxide dismutase was measured by the polarographic method of catalytic currents in the cerebrospinal fluid of patients with age-related neurologic degenerative diseases, namely, amyotrophic lateral sclerosis and Alzheimer's disease, and of a reference group of normal subjects. The superoxide dismutase activity was found to increase with age in reference subjects (r = 0.81) while no significant correlation was found in amyotrophic lateral sclerosis and Alzheimer's disease patients. The activity mean values were significantly lower (P less than 0.01) in patients with neurologic degenerative diseases than in the reference subjects. The changes of superoxide dismutase activity in the aging brain and in age-related neurologic degenerative diseases are discussed.

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Effect of ionic strength on the activity of bovine superoxide dismutase

Cited by 46 publications

References 11 publications

Phosphate is an inhibitor of copper-zinc superoxide dismutase

Phosphate is an inhibitor of copper-zinc superoxide dismutase

Hypoxia-generated superoxide induces the development of the adhesion phenotype

Determination of Superoxide Dismutase Activity by the Polarographic Method of Catalytic Currents in the Cerebrospinal Fluid of Aging Brain and Neurologic Degenerative Diseases

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