Glutathione Peroxidase, V. The kinetic mechanism

Flohé, Leopold; Loschen, G.; Günzler, Wolfgang A.; Eichele, Erich

doi:10.1515/bchm2.1972.353.1.987

Cited by 333 publications

(194 citation statements)

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“…Glutathione peroxidase was prepared according to [9]. All other enzymes as well as all coenzymes, GSSG and Na-pyruvate were from Boehringer, Mannheim.…”

Section: Methodsmentioning

confidence: 99%

Oxidation in the NADP system and release of GSSG from hemoglobin‐free perfused rat liver during peroxidatic oxidation of glutathione by hydroperoxides

et al. 1972

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“…Glutathione peroxidase was prepared according to [9]. All other enzymes as well as all coenzymes, GSSG and Na-pyruvate were from Boehringer, Mannheim.…”

Section: Methodsmentioning

confidence: 99%

Oxidation in the NADP system and release of GSSG from hemoglobin‐free perfused rat liver during peroxidatic oxidation of glutathione by hydroperoxides

et al. 1972

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“…In the case of hydrogen peroxide, another possible target is glutathione peroxidase 3, which, at a concentration of 175 nM, reacts with a rate constant of 1.8 x 10 8 M -1 s -1 (20,21). However, the scarcity of glutathione in plasma questions its significance in vivo.…”

Section: Reactivity Of the Albumin Thiolmentioning

confidence: 99%

Oxidation of the albumin thiol to sulfenic acid and its implications in the intravascular compartment

Turell

Carballal

Botti

et al. 2009

Braz J Med Biol Res

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Human serum albumin (HSA) is the most abundant protein in the intravascular compartment. It possesses a single thiol, Cys34, which constitutes ~8 0% of the total thiols in plasma. This thiol is able to scavenge plasma oxidants. A central intermediate in this potential antioxidant activity of human serum albumin is sulfenic acid (HSA-SOH). Work from our laboratories has demonstrated the formation of a relatively stable sulfenic acid in albumin through complementary spectrophotometric and mass spectrometric approaches. Recently, we have been able to obtain quantitative data that allowed us to measure the rate constants of sulfenic acid reactions with molecules of analytical and biological interest. Kinetic considerations led us to conclude that the most likely fate for sulfenic acid formed in the plasma environment is the reaction with low molecular weight thiols to form mixed disulfides, a reversible modification that is actually observed in ~2 5% of circulating albumin. Another possible fate for sulfenic acid is further oxidation to sulfinic and sulfonic acids. These irreversible modifications are also detected in the circulation. Oxidized forms of albumin are increased in different pathophysiological conditions and sulfenic acid lies in a mechanistic junction, relating oxidizing species to final thiol oxidation products.

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“…Because no saturation of glutathione peroxidase by GSH can be achieved (22,23,24), the enzymatic reaction rate follows at least pseudo first order kinetics. Whenever a spontaneous reaction of a comparable velocity competes with this enzymatic reaction, the application of the fixed time assay procedure must necessarily result in ambiguous values of enzyme activity (25,17).…”

Section: Kinetic Considerations Concerning the Assaymentioning

confidence: 99%

“…Complete saturation of glutathione peroxidase, however, proved not to be advisable, because the spontaneous reaction rates will be enhanced by increasing hydroperoxide concentrations. On the other hand, in the assay proposed by Pagtia & Valentine (10) hydroperoxide is employed at 3 times K m ( app ) concentration (10,22,23), a concentration far too low to result in a constant enzymatic reaction rate. Only 75% maximum velocity of the enzymatic reaction rate can initially be expected by this procedure.…”

Section: Kinetic Considerations Concerning the Assaymentioning

confidence: 99%

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An Improved Coupled Test Procedure for Glutathione Peroxidase (EC 1.11.1.9.) in Blood

Günzler¹,

Kremers²,

Flohé³

1974

Clinical Chemistry and Laboratory Medicine

238

159

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An optimized coupled test system for glutathione peroxidase in red blood cells is presented. In the improved assay, tert. butyl hydroperoxide was employed as an acceptor substrate at twenty times K m ( app ) concentration. By aid of a batching procedure for instant separation of hemoglobin from glutathione peroxidase, it could be proved that cyanmethemoglobin in the modified procedure does not affect the spontaneous reaction rate. Further possible interference with the determination could be excluded. Glutathione peroxidase activities in red blood cells of normal adults were measured by the improved test method. A glutathione peroxidase activity in human plasma was observed.

show abstract

Glutathione Peroxidase, V. The kinetic mechanism

Cited by 333 publications

References 0 publications

Oxidation in the NADP system and release of GSSG from hemoglobin‐free perfused rat liver during peroxidatic oxidation of glutathione by hydroperoxides

Oxidation in the NADP system and release of GSSG from hemoglobin‐free perfused rat liver during peroxidatic oxidation of glutathione by hydroperoxides

Oxidation of the albumin thiol to sulfenic acid and its implications in the intravascular compartment

An Improved Coupled Test Procedure for Glutathione Peroxidase (EC 1.11.1.9.) in Blood

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