Enzymes and Metabolites of Cysteine Metabolism in Nonhepatic Tissues of Rats Show Little Response to Changes in Dietary Protein or Sulfur Amino Acid Levels

Stipanuk, Martha H.; Londono, Monica; Lee, Jeong-In; Hu, Mindy; Yu, Anthony F.

doi:10.1093/jn/132.11.3369

Cited by 120 publications

(133 citation statements)

References 38 publications

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“…However, intracellular cysteine levels are much lower, about 25 μM in normal cells [37], and presumably far lower than this in cells with cysteine-responsive GSH depletion. Moreover, CSF concentrations do not indicate the rate of NAC flux from plasma to the neuronal intracellular space.…”

Section: Discussionmentioning

confidence: 91%

Neuronal Glutathione Content and Antioxidant Capacity can be Normalized In Situ by N-acetyl Cysteine Concentrations Attained in Human Cerebrospinal Fluid

et al. 2016

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N-acetyl cysteine (NAC) supports the synthesis of glutathione (GSH), an essential substrate for fast, enzymatically catalyzed oxidant scavenging and protein repair processes. NAC is entering clinical trials for adrenoleukodystrophy, Parkinson's disease, schizophrenia, and other disorders in which oxidative stress may contribute to disease progression. However, these trials are hampered by uncertainty about the dose of NAC required to achieve biological effects in human brain. Here we describe an approach to this issue in which mice are used to establish the levels of NAC in cerebrospinal fluid (CSF) required to affect brain neurons. NAC dosing in humans can then be calibrated to achieve these NAC levels in human CSF. The mice were treated with NAC over a range of doses, followed by assessments of neuronal GSH levels and neuronal antioxidant capacity in ex vivo brain slices. Neuronal GSH levels and antioxidant capacity were augmented at NAC doses that produced peak CSF NAC concentrations of ≥50 nM. Oral NAC administration to humans produced CSF concentrations of up to 10 μM, thus demonstrating that oral NAC administration can surpass the levels required for biological activity in brain. Variations of this approach may similarly facilitate and rationalize drug dosing for other agents targeting central nervous system disorders.

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Section: Discussionmentioning

confidence: 91%

Neuronal Glutathione Content and Antioxidant Capacity can be Normalized In Situ by N-acetyl Cysteine Concentrations Attained in Human Cerebrospinal Fluid

et al. 2016

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“…Structure Determination and Refinement-Initial analysis of the collected x-ray diffraction data indicated alternative possibilities of space groups P6 1 and P6 5 . Molecular replacement calculations confirmed the latter space group, P6 5 , as the correct one for the crystal of human CDO in complex with the substrate cysteine.…”

Section: Resultsmentioning

confidence: 99%

An Insight into the Mechanism of Human Cysteine Dioxygenase

Ye¹,

Wu²,

Wei³

et al. 2007

Journal of Biological Chemistry

165

131

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Cysteine dioxygenase is a non-heme mononuclear iron metalloenzyme that catalyzes the oxidation of cysteine to cysteine sulfinic acid with addition of molecular dioxygen. This irreversible oxidative catabolism of cysteine initiates several important metabolic pathways related to diverse sulfurate compounds. Cysteine dioxygenase is therefore very important for maintaining the proper hepatic concentration of intracellular free cysteine. Mechanisms for mouse and rat cysteine dioxygenases have recently been reported based on their crystal structures in the absence of substrates, although there is still a lack of direct evidence. Here we report the first crystal structure of human cysteine dioxygenase in complex with its substrate L-cysteine to 2.7 Å , together with enzymatic activity and metal content assays of several single point mutants. Our results provide an insight into a new mechanism of cysteine thiol dioxygenation catalyzed by cysteine dioxygenase, which is tightly associated with a thioether-bonded tyrosine-cysteine cofactor involving Tyr-157 and Cys-93. This cross-linked protein-derived cofactor plays several key roles different from those in galactose oxidase. This report provides a new potential target for therapy of diseases related to human cysteine dioxygenase, including neurodegenerative and autoimmune diseases.Cysteine dioxygenase (CDO, 2 EC 1.13.11.20) is a non-heme mononuclear iron metalloenzyme that catalyzes the irreversible oxidation of cysteine to cysteine sulfinic acid (CSA) with addition of molecular oxygen (1) (Structure 1). This oxidative catabolism of cysteine initiates several important metabolic pathways related to pyruvate and several sulfurate compounds, including sulfate, hypotaurine, and taurine. CDO is expressed at appreciable levels in the brain, kidney, and lung, with extremely high levels in liver tissue (2-5), where CDO plays an important role in maintaining the hepatic concentration of intracellular free cysteine within a proper narrow range (6). When the levels of cysteine decrease below this range, the increase of CDO ubiquitination rate results in rapid degradation of the ubiquitinated portion by the 26 S proteasome system (7,8). However, the precise means by which cysteine regulates CDO ubiquitination remain unknown.Intracellular free cysteine is cytotoxic and neuroexcitotoxic due to oxidative damage via formation of free radicals in the presence of iron (9 -11). Elevated cysteine levels were reported previously in relation to several neurodegenerative diseases, including the well known Parkinson and Alzheimer diseases (12-14), and autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis (15, 16). CDO is considered to be involved in these diseases due to its function in regulating free cysteine levels.Sequence alignment classifies CDO as a member of the cupin superfamily (see Fig. 1), whose members possess what may be the most diverse range of functions, encompassing ϳ18 subclasses. Nonetheless, neither of the exact characteristic conserved sequenc...

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“…Homocysteine concentration in mammalian tissues is estimated to be *1-10 lM (18), while the concentration of cysteine is *100 lM in liver and brain, and up to 1.0 mM in kidney (37,40). Kinetic data and simulation analyses indicate that at physiologically relevant substrate concentrations (10 lM homocysteine and 100 lM cysteine), CBS generates H 2 S mainly via condensation of cysteine and homocysteine while CSE generates H 2 S primarily via a,b-replacement of cysteine (7,34).…”

mentioning

confidence: 99%

High Turnover Rates for Hydrogen Sulfide Allow for Rapid Regulation of Its Tissue Concentrations

Vitvitsky

Kabil

Banerjee

2012

Antioxidants & Redox Signaling

176

169

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Aims: Hydrogen sulfide (H 2 S) is a signaling molecule, which influences many physiological processes. While H 2 S is produced and degraded in many cell types, the kinetics of its turnover in different tissues has not been reported. In this study, we have assessed the rates of H 2 S production in murine liver, kidney, and brain homogenates at pH 7.4, 37°C, and at physiologically relevant cysteine concentrations. We have also studied the kinetics of H 2 S clearance by liver, kidney, and brain homogenates under aerobic and anaerobic conditions. Results: We find that the rate of H 2 S production by these tissue homogenates is considerably higher than background rates observed in the absence of exogenous substrates. An exponential decay of H 2 S with time is observed and, as expected, is significantly faster under aerobic conditions. The half-life for H 2 S under aerobic conditions is 2.0, 2.8, and 10.0 min with liver, kidney, and brain homogenate, respectively. Western-blot analysis of the sulfur dioxygenase, ETHE1, involved in H 2 S catabolism, demonstrates higher steady-state protein levels in liver and kidney versus brain. Innovation: By combining experimental and simulation approaches, we demonstrate high rates of tissue H 2 S turnover and provide estimates of steady-state H 2 S levels. Conclusion: Our study reveals that tissues maintain a high metabolic flux of sulfur through H 2 S, providing a rationale for how H 2 S levels can be rapidly regulated. Antioxid. Redox Signal. 17, 22-31.

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Enzymes and Metabolites of Cysteine Metabolism in Nonhepatic Tissues of Rats Show Little Response to Changes in Dietary Protein or Sulfur Amino Acid Levels

Cited by 120 publications

References 38 publications

Neuronal Glutathione Content and Antioxidant Capacity can be Normalized In Situ by N-acetyl Cysteine Concentrations Attained in Human Cerebrospinal Fluid

Neuronal Glutathione Content and Antioxidant Capacity can be Normalized In Situ by N-acetyl Cysteine Concentrations Attained in Human Cerebrospinal Fluid

An Insight into the Mechanism of Human Cysteine Dioxygenase

High Turnover Rates for Hydrogen Sulfide Allow for Rapid Regulation of Its Tissue Concentrations

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