Blood glutathione synthesis rates in healthy adults receiving a sulfur amino acid-free diet

Lyons, Jeremy; Rauh-Pfeiffer, Astrid A. M.; Yu, Yong‐Ming; Lu, Xiaoming; Zurakowski, David; Tompkins, Ronald G.; Ajami, Alfred M.; Young, Vernon R.; Castillo, Leticia

doi:10.1073/pnas.090083297

Cited by 143 publications

(123 citation statements)

References 35 publications

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“…At prevailing concentrations of GSH (2 M) and CySS (40 M) in plasma (84), the calculated rate of reaction of GSH with CySS is 0.0016 mol⅐l Ϫ1 ⅐min Ϫ1 . This is much lower than the rate of Cys turnover in humans, which was determined by stable isotopic tracer methods to be about 1 mol⅐kg Ϫ1 ⅐min Ϫ1 (47,115,144). Thus the calculated rates are consistent with measured steady-state redox values showing that the rates of thiol-disulfide exchange are too slow to allow redox couples to equilibrate in human plasma.…”

Section: Nonequilibrium Conditions Of Thiol-disulfide Couples In Biolsupporting

confidence: 74%

Radical-free biology of oxidative stress

Jones¹

2008

American Journal of Physiology-Cell Physiology

991

815

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Free radical-induced macromolecular damage has been studied extensively as a mechanism of oxidative stress, but large-scale intervention trials with free radical scavenging antioxidant supplements show little benefit in humans. The present review summarizes data supporting a complementary hypothesis for oxidative stress in disease that can occur without free radicals. This hypothesis, which is termed the "redox hypothesis," is that oxidative stress occurs as a consequence of disruption of thiol redox circuits, which normally function in cell signaling and physiological regulation. The redox states of thiol systems are sensitive to twoelectron oxidants and controlled by the thioredoxins (Trx), glutathione (GSH), and cysteine (Cys). Trx and GSH systems are maintained under stable, but nonequilibrium conditions, due to a continuous oxidation of cell thiols at a rate of about 0.5% of the total thiol pool per minute. Redox-sensitive thiols are critical for signal transduction (e.g., H-Ras, PTP-1B), transcription factor binding to DNA (e.g., Nrf-2, nuclear factor-B), receptor activation (e.g., ␣IIb␤3 integrin in platelet activation), and other processes. Nonradical oxidants, including peroxides, aldehydes, quinones, and epoxides, are generated enzymatically from both endogenous and exogenous precursors and do not require free radicals as intermediates to oxidize or modify these thiols. Because of the nonequilibrium conditions in the thiol pathways, aberrant generation of nonradical oxidants at rates comparable to normal oxidation may be sufficient to disrupt function. Considerable opportunity exists to elucidate specific thiol control pathways and develop interventional strategies to restore normal redox control and protect against oxidative stress in aging and age-related disease.thioredoxin; glutathione; cysteine; hydrogen peroxide; redox signaling; protein thiol ONE OF THE GREAT REDOX BIOLOGISTS of the past century, Howard S. Mason, professed that to advance science, a scientist must interpret observations at the limit of their meaning. The present review of the redox biology of thiol systems addresses the possibility that disruption of the function and homeostasis of thiol systems is the most central feature of oxidative stress that contributes to mechanisms of aging and age-related disease. I have termed this the "redox hypothesis" to facilitate distinction from free radical hypotheses.Many proteins contain redox-sensitive thiols, and reactions of thiol systems occur largely by nonradical two-electron transfers. Accumulating data show that central thiol-disulfide couples are maintained under nonequilibrium conditions in biological systems. This presents a condition wherein changes in abundance and distribution of redox catalysts and changes in rates of generation of relevant oxidants (e.g., peroxides) and precursors for NADPH supply can account for pathological effects of oxidative stress through altered functions of enzymes, receptors, transporters, transcription factors, and structural elements, without free ra...

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Section: Nonequilibrium Conditions Of Thiol-disulfide Couples In Biolsupporting

confidence: 74%

Radical-free biology of oxidative stress

Jones¹

2008

American Journal of Physiology-Cell Physiology

991

815

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“…6D). It is more likely, as has been reported for rodents and human (55,56), that the availability, in the case of P. multocida, of the essential amino acid L-Cys may be the rate-limiting factor for glutathione synthesis. Glutathione feedback inhibition then comes into play when the environment is loaded with physiologically relevant (low micromolar) levels of glutathione, because the accumulation of the tripeptide by means of active transport not only inhibits GshF but also indirectly should increase the rate of L-Cys availability.…”

Section: Discussionmentioning

confidence: 84%

Characterization of the Bifunctional γ-Glutamate-cysteine Ligase/Glutathione Synthetase (GshF) of Pasteurella multocida

Vergauwen

Vos

Beeumen

2006

Journal of Biological Chemistry

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Glutamate-cysteine ligase (␥-ECL) and glutathione synthetase (GS) are the two unrelated ligases that constitute the glutathione biosynthesis pathway in most eukaryotes, purple bacteria, and cyanobacteria. ␥-ECL is a member of the glutamine synthetase family, whereas GS enzymes group together with highly diverse carboxylto-amine/thiol ligases, all characterized by the so-called two-domain ATP-grasp fold. This generalized scheme toward the formation of glutathione, however, is incomplete, as functional steadystate levels of intracellular glutathione may also accumulate solely by import, as has been reported for the Pasteurellaceae member Haemophilus influenzae, as well as for certain Gram-positive enterococci and streptococci, or by the action of a bifunctional fusion protein (termed GshF), as has been reported recently for the Gram-positive firmicutes Streptococcus agalactiae and Listeria monocytogenes. Here, we show that yet another member of the Pasteurellaceae family, Pasteurella multocida, acquires glutathione both by import and GshF-driven biosynthesis. Domain architecture analysis shows that this P. multocida GshF bifunctional ligase contains an N-terminal ␥-proteobacterial ␥-ECL-like domain followed by a typical ATP-grasp domain, which most closely resembles that of cyanophycin synthetases, although it has no significant homology with known GS ligases. Recombinant P. multocida GshF overexpresses as an ϳ85-kDa protein, which, on the basis of gel-sizing chromatography, forms dimers in solution. The ␥-ECL activity of GshF is regulated by an allosteric type of glutathione feedback inhibition (K i ‫؍‬ 13.6 mM). Furthermore, steady-state kinetics, on the basis of which we present a novel variant of half-of-the-sites reactivity, indicate intimate domain-domain interactions, which may explain the bifunctionality of GshF proteins.Glutathione (GSH; L-␥-glutamyl-L-cysteinylglycine) is the predominant low molecular weight peptide thiol present in many Gram-negative bacteria and in virtually all eukaryotes, except those that lack mitochondria (1, 2). Glutathione is made in a highly conserved two-step ATP-dependent biosynthesis pathway by two unrelated peptide bondforming enzymes (3). In the first and rate-limiting reaction, ␥-glutamate-cysteine ligase (␥-ECL) 2 (EC 6.3.2.2) condenses the ␥-carboxylate of L-glutamic acid with L-cysteine to form the dipeptide ␥-glutamylcys-where Me 2ϩ can be magnesium or manganese (4, 5). In the second step, ␥-EC is condensed with glycine in a reaction catalyzed by glutathione synthetase (GS; EC 6.3.2.3), according towhere Me 2ϩ again can be magnesium or manganese. The activity of eukaryotic ␥-ECL is precisely controlled by nonallosteric glutathione feedback inhibition, the limited availability of cellular L-Cys, and the transcriptional and posttranslational regulation of the expression and activity of the enzyme under various physiological conditions (6). Bacterial glutathione homeostasis is less well characterized, although glutathione feedback inhibition appears to be of major importa...

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“…Overall, pediatric patients with sepsis show impairment in erythrocyte antioxidant defenses. Erythrocytes are the second most important source of GSH after the liver, accounting for a 10% of total body GSH production [26]. Red cell oxidative damage can alter its deformability and cause premature aging and lower oxygen transport capability [27], which is of vital relevance in the context of septic shock.…”

Section: Discussionmentioning

confidence: 99%

Oxidative stress biomarkers in pediatric sepsis: a prospective observational pilot study

et al. 2016

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Objectives: Oxidative stress is known to participate in the progression of sepsis. Definite data regarding the behavior of oxidative stress biomarkers in pediatric sepsis is still lacking. This study hypothesized that oxidative stress occurs in pediatric sepsis and that the magnitude of the redox derangement is associated with worse clinical progression. Methods: Forty-two previously healthy pediatric patients with sepsis and a group of control subjects were included. Oxidative stress and inflammatory activity biomarkers were determined in blood samples. Patients were prospectively followed until their discharge or death. Results: Patients with non-severe and severe sepsis showed higher levels of plasmatic antioxidant capacity, lower erythrocyte thiol index, lower superoxide dismutase and catalase activities, higher glutathione peroxidase activity, and higher plasmatic F 2 -isoprostanes concentration than controls. Patients with severe sepsis had higher NF-kappaB activation than those with non-severe sepsis. Although we observed changes in some biomarkers in patients with worse clinical evolution, the explored biomarkers did not correlate with clinical estimators of outcome. Discussion: Oxidative stress occurs in pediatric sepsis, resulting in oxidative damage. The explored biomarkers are not useful as outcome predictors in the studied population. The behavior of these biomarkers still needs to be addressed in broader groups of pediatric patients with sepsis.

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Blood glutathione synthesis rates in healthy adults receiving a sulfur amino acid-free diet

Cited by 143 publications

References 35 publications

Radical-free biology of oxidative stress

Radical-free biology of oxidative stress

Characterization of the Bifunctional γ-Glutamate-cysteine Ligase/Glutathione Synthetase (GshF) of Pasteurella multocida

Oxidative stress biomarkers in pediatric sepsis: a prospective observational pilot study

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