摘要:

The glutathione S-transferase (GST) supergene family comprises gene families that encode isoenzymes that are widely expressed in mammalian tissue cytosols and membranes. Both cytosolic (particularly the isoenzymes encoded by the alpha, mu and theta gene families) and microsomal GST catalyse the conjugation of reduced glutathione (GSH) with a wide variety of electrophiles which include known carcinogens as well as various compounds that are products of oxidative stress including oxidised DNA and lipid. Indeed, several lines of evidence suggest certain of these isoenzymes play a pivotal role in protecting cells from the consequences of such stress. An assessment of the importance of these GST in humans is presently difficult however, because the number of alpha and theta class genes is not known and, the catalytic preferences of even identified isoforms is not always clear.

ISSN:1071-5762    

DOI:10.3109/10715769509147539

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

In vivoantioxidant activity seems to be quite complicate due to multiple interaction with biomaterials and differs from results byin vitroexperiments.In vivoestimation of antioxidant activity is performed by measuring TBA reactive substances in blood or hydrocarbon gases in breath, but these systems do not measure free radical reaction but the final products of oxidative reaction. In the present study, we appliedin vivoESR to evaluate antioxidant activity by monitoring the redox reaction of nitroxide radical and clearly found that the nitroxide is very susceptible to oxidative stressin vivoand quite useful to evaluate antioxidant activity non-invasively.

ISSN:1071-5762    

DOI:10.3109/10715769509147540

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The mechanism of myoglobin/H2O2derived peroxidation of myosin was studied by comparing the catalytic activity of myoglobin and horseradish peroxidase using O-dianisidine, N-acetyl tyrosine and myosin as substrates. It was found that both hemoproteins induced myosin crosslinking and concomitant tyrosines oxidation to bityrosines, suggesting inter-molecular coupling of tyrosines in the crosslinking. The enzymatic activity of both hemoproteins on myosin was weak compared to small substrates. While horseradish peroxidase was much more active than myoglobin on small substrates, the reverse was true for myosin peroxidation. Since the suicidal interaction of myoglobin with H2O2forms unstable tyrosine radicals, we suggest that the increased activity of myoglobin on myosin results from an efficient electron transfer between surface tyrosines of myosin and myoglobin but not horseradish peroxidase. These conclusions were supported by evidence that sperm whale myoglobin, which contains two active tyrosines -the heme-adjacent (tyrosine-103) and the surface (tyrosine-151), is more active as a mediator of myosin peroxidation than horse heart myoglobin which is devoid of the surface tyrosine.

ISSN:1071-5762    

DOI:10.3109/10715769509147541

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The effects of active oxygen species on thein vivoactivity of recombinant human erythropoietin (EPO) treated by Fenton system, xanthine (X) plus xanthine oxidase (XO) system and hydrogen peroxide (H2O2) has been studied by means of counting the increase in number of hemolyser-resistant cells (HRCs) in EPO-injected mice. The results showed that both Fenton and X plus XO systems caused a significant reduction of the activity in proportion to the concentration of generated active oxygen species. Meanwhile, the treatment of EPO with H2O2alone resulted in a relatively slight reduction of the activity. Electrophoretic studies on the structure of EPO revealed that its main protein band on sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) disappeared in proportion with the extent of exposure to active oxygen generating systems. Both Fenton and X plus XO systems caused a significant loss of fluorescence in the pyridylamino (PA-) sugar chain in proportion to the concentration of generated active oxygen species, and no degradation products in the sugar chain part of the PA-sugar chain were detected. This showed that aromatic groups in EPO were sensitive to attack by active oxygen species. These results provide evidence that hydroxyl radical and other active oxygen species have a potential to react with EPO, leading to a reduction of itsin vivoactivity.

ISSN:1071-5762    

DOI:10.3109/10715769509147542

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Copper Fenton systems (Cu(II)/H2O2and Cu(II)/Asc) inactivated the lipoamide reductase and enhanced the diaphorase activity of pig-heart lipoamide dehydrogenase (LADH). Cupric ions alone were less effective. As a result of Cu(II)/H2O2treatment, the number of titrated thiols in LADH decreased from 6 to 1 per subunit. NADH and ADP (not NAD+or ATP) enhanced LADH inactivation by Cu(II). NADH also enhanced the effect of Cu(II)/H2O2. Dihydrolipoamide, dihydrolipoic acid, Captopril, acetylcysteine, EDTA, DETAPAC, histidine, bathocuproine, GSSG and trypanothione prevented LADH inactivation. 100μM GSH, DL-dithiothreitol, N-(2-mercaptopropionylglicine) and penicillamine protected LADH against Cu(II)/Asc and Cu(II), whereas 1.0 mm GSH and DL-dithiothreitol also protected LADH against Cu(II)/H2O2. Allopurinol provided partial protection against Cu(II)/H2O2. EthanoI, mannitol, Na benzoate and superoxide dismutase failed to prevent LADH inactivation by Cu(II)/H2O2or Cu(II). Catalase (native or denaturated) and bovine serum albumin protected LADH but that protection should be due to Cu binding. LADH inhibited deoxyribose oxidation and benzoate hydroxylation by Cu(II)/H2O2. It is concluded that site-specifically generated HO, radicals were responsible for LADH inactivation by Cu(II) Fenton systems. The latter effect is discussed in the context of ischemia-reoxygenation myocardial injury.

ISSN:1071-5762    

DOI:10.3109/10715769509147543

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The oxidized intermediates generated upon exposure of bovine liver catalase to hydrogen peroxide (H2O2) and superoxide radical (OJ) fluxes were examined with UV-visible spectrophotometry. H2O2and O2−were generated by means of glucose/glucose oxidase and xanthine/xanthine oxidase systems. Serial overlay of absorption spectra in the Soret (350-450 nm) and visible (450-700 nm) regions showed that three oxidized intermediates, namely Compounds I, II and III, can be observed upon exposure of catalase to enzymatically generated H2O2and O2−. Compound I is formed during the reaction of native enzyme with H2O2and disappears in two ways: (i) via the catalytic reaction with H2O2to restore native catalase and (ii) via the reaction with OJ to form Compound II. At low H2O2concentrations (<4.8×10−9M H2O2), Compound II reverts towards the native state mainly in a direct one-step reaction, whereas at higher H2O2concentrations the pathway of Compound II back to the native enzyme involves Compound III. Formation of the latter from Compound II and H2O2is irreversible and the rate constant of this reaction is 6.1±0.2×104M−1s−1. The formation of Compound III through the direct reaction of OJ with native enzyme has also been observed. Depending on the experimental conditions, the inactivation of catalase by OJ can be due to accumulation of Compound II (“slow”inhibition) or to the formation of Compound III (“rapid”inhibition) part of which leads to a dead end product. Formation of Compound III and of this dead end product are responsible for the irreversible inactivation in presence of an excess of H2O2.

ISSN:1071-5762    

DOI:10.3109/10715769509147544

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Cystine markedly enhanced the cytotoxic response ofEscherichia colicells to concentrations of hydrogen peroxide resulting in mode one killing, but displayed little effect in mode two killed cells. The effect of cystine was concentration-dependent over a range of 5-50μM and did not further increase at higher levels. Cystine had similar effects in other bacterial systems.In order to sensitize the cells to the oxidative injury, the amino acid must be present during exposure to the oxidant since no enhancement of the cytotoxic response can be observed in cystine pre-loaded cells. In addition, no further enhancement of cytotoxicity could be detected when cystine was added before and left during challenge with the oxidant. The enhancing effect of cystine on oxidative injury ofE. colicells appears to be directly mediated by the amino acid and in fact cysteic acid, the most likely oxidation product, had no effect on the killing of bacterial cells elicited by hydrogen peroxide. Other disulfide compounds such as oxidized glutathione, cystamine and dithionitrobenzoic acid only slightly increased the susceptibility of bacteria to the oxidant. The effect of the disulfides was not concentration-dependent over a range of 200-800μM and was statistically significant only for cystamine.Taken together, these results indicate that cystine markedly increases the cytotoxic response of bacteria to hydrogen peroxide and suggest that the amino acid might impair the cellular defence machinery against hydrogen peroxide. This effect may involve a thiol-disulfide exchange reaction at the cell membrane level.

ISSN:1071-5762    

DOI:10.3109/10715769509147545

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The Retinoids, Biology, Chemistry, and Medicine Second Edition, Ed. by M.B. Sporn, A.B. Roberts and De W.S. Goodman Raven Press, New York. 1994. pp. 699, price US$200.50Free Radicals: From Basic Science to Medicine Edited by G. Poli, M. Albano and M.U. DianzaniMolecular Biology Update SeriesBirkhauser Verlag pp528. Price: 148 SFrThe Development of Iron Chelators for Clinical Use R.J. Bergeeron, G.M. Brittenham (Eds).CRC Press: Boca Raton. 1994 pp 416 ISBN 0-8493-8679-9

ISSN:1071-5762    

DOI:10.3109/10715769509147546

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769509147547

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor