Formation of thiocarbonyl compounds in the reaction of Ebselen oxide with thiols

Glass, Richard S.; Farooqui, Firdous; Sabahi, M.; Ehler, Kenneth W.

doi:10.1021/jo00266a018

Cited by 66 publications

(28 citation statements)

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“…The reaction yield was 91% and was Ն95% pure as determined by HPLC with UV detection at 220 nm. Identity of NASBC was also confirmed by 1 H NMR, and the chemical shifts match well with what has been reported in the literature (Glass et al, 1989).…”

Section: Methodssupporting

confidence: 89%

Sulfoxides as Urinary Metabolites ofS-Allyl-l-Cysteine in Rats: Evidence for the Involvement of Flavin-Containing Monooxygenases

Krause¹,

Glocke²,

Elfarra³

2002

Drug Metab Dispos

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ABSTRACT:S-Allyl-L-cysteine (SAC), a component of garlic and a metabolite of allyl halides, is a known substrate for multiple flavin-containing monooxygenases (FMOs). In the current study, we characterize the in vivo SAC metabolism by investigating the presence of SAC, N-acetyl-S-allyl-L-cysteine (NASAC), and their corresponding sulfoxides in the urine of rats given SAC (200 or 400 mg/kg i.p.). In some experiments, rats were given aminooxyacetic acid (AOAA), an inhibitor of cysteine conjugate ␤-lyase, or methimazole, an alternative FMO substrate, 30 min prior to treatment with 200 mg/kg SAC. Nearly 40 to 50% of the dose was recovered in the 24-h collection period. In all treatment groups, the majority of the metabolites were excreted within 8 h. The major metabolites detected were NASAC and NASAC sulfoxide (NASACS; nearly 30-40% and 5-10% of the dose, respectively). Only small amounts of the dose (approximately 1.5%) were recovered as SAC and SAC sulfoxide (SACS). Methimazole pretreatment significantly reduced amounts of both SACS and NASACS detected in the urine when compared with rats given SAC only, whereas AOAA pretreatment had no effect. In vitro assays using rat liver microsomes were also carried out to compare the sulfoxidation rates of SAC and NASAC. The results showed that SAC was much more readily oxidized than NASAC. Collectively, the results provide evidence for the involvement of FMOs in the in vivo metabolism of SAC and that SAC is a much better substrate for FMOs than its corresponding mercapturic acid. (SAC 1 ) is a significant water-soluble allyl sulfur component in garlic preparations (Weinberg et al., 1993), a component which has been shown to have antioxidant and anticancer properties in animals (Sumiyoshi and Wargovich, 1990;Hatono et al., 1996;Ho et al., 2001). SAC has been shown to have antiproliferative effects on neuroblastoma (Welch et al., 1992), melanoma (Takeyama et al., 1993), and prostate carcinoma cells (Pinto et al., 1997). However, the mechanisms of the anticancer properties of SAC are unclear. S-Allyl-L-cysteineSAC is also a known metabolite of allyl halides and allyl esters, including allyl chloride, allyl bromide, sodium allyl sulfate, and allyl nitrate (Kaye et al., 1972;Kaye, 1973). It results from the formation of the glutathione conjugate of the allyl halide or ester. The glutamate and glycine moieties of S-allyl-glutathione are then cleaved by ␥-glutamyl transpeptidase and dipeptidases to yield SAC.Our laboratory has previously shown that SAC is a substrate for multiple rabbit and human flavin-containing monooxygenases (FMOs). FMOs are microsomal enzymes that catalyze the NADPHdependent oxidation of many compounds that contain sulfur, nitrogen, selenium, and phosphorus (Ziegler, 1993). Previously, we have shown that SAC is metabolized to the greatest extent by cDNA-expressed rabbit FMO3 followed by FMO1 and then FMO2, but SAC showed no activity with rabbit FMO5 (Ripp et al., 1997). More recently and using cDNA-expressed human FMOs, SAC has been shown to be a good substr...

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Section: Methodssupporting

confidence: 89%

Sulfoxides as Urinary Metabolites ofS-Allyl-l-Cysteine in Rats: Evidence for the Involvement of Flavin-Containing Monooxygenases

Krause¹,

Glocke²,

Elfarra³

2002

Drug Metab Dispos

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“…Remarkably, when EbO was incubated with WspR for 30 minutes, the molecular weight was the same as WspR treated with Eb (Figure 5D). This suggests that EbO was being reduced either by the protein or the assay buffer to Eb and covalently linked to WspR 41 . We tested whether WspR enzymatic activity is required to convert EbO to Eb and found the ratio of EbO to Eb to be the same in the heat-killed WspR compared with the untreated protein.…”

Section: Resultsmentioning

confidence: 99%

High-Throughput Screening Using the Differential Radial Capillary Action of Ligand Assay Identifies Ebselen As an Inhibitor of Diguanylate Cyclases

et al. 2013

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The rise of bacterial resistance to traditional antibiotics has motivated recent efforts to identify new drug candidates that target virulence factors or their regulatory pathways. One such antivirulence target is the cyclic-di-GMP (cdiGMP) signaling pathway, which regulates biofilm formation, motility, and pathogenesis. Pseudomonas aeruginosa is an important opportunistic pathogen that utilizes cdiGMP-regulated polysaccharides, including alginate and pellicle polysaccharide (PEL), to mediate virulence and antibiotic resistance. CdiGMP activates PEL and alginate biosynthesis by binding to specific receptors including PelD and Alg44. Mutations that abrogate cdiGMP binding to these receptors prevent polysaccharide production. Identification of small molecules that can inhibit cdiGMP binding to the allosteric sites on these proteins could mimic binding defective mutants and potentially reduce biofilm formation or alginate secretion. Here, we report the development of a rapid and quantitative high-throughput screen for inhibitors of protein-cdiGMP interactions based on the differential radial capillary action of ligand assay (DRaCALA). Using this approach, we identified ebselen as an inhibitor of cdiGMP binding to receptors containing an RxxD domain including PelD and diguanylate cyclases (DGC). Ebselen reduces diguanylate cyclase activity by covalently modifying cysteine residues. Ebselen oxide, the selenone analogue of ebselen, also inhibits cdiGMP binding through the same covalent mechanism. Ebselen and ebselen oxide inhibit cdiGMP regulation of biofilm formation and flagella-mediated motility in P. aeruginosa through inhibition of diguanylate cyclases. The identification of ebselen provides a proof-of-principle that a DRaCALA high-throughput screening approach can be used to identify bioactive agents that reverse regulation of cdiGMP signaling by targeting cdiGMP-binding domains.

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“…A more detailed analysis as to whether peroxynitrite or peroxynitrous acid or both react with GPx under a given condition would require the use of stopped-flow methods. The subsequent two steps in the reaction cycle are facile regeneration reactions at the expense of reducing equivalents provided by GSH in cells, as known from the extensive work on GPx (24), and as studied with ebselen selenoxide (27)(28)(29)(30). Regarding the chemical mechanism, it might be concluded that the selenolate form of the selenocysteine residue is required.…”

Section: Discussionmentioning

confidence: 99%

Glutathione Peroxidase Protects against Peroxynitrite-mediated Oxidations

Sies

Sharov²,

Klotz

et al. 1997

Journal of Biological Chemistry

445

206

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There is a requirement for cellular defense against excessive peroxynitrite generation to protect against DNA strand breaks and mutations and against interference with protein tyrosine-based signaling and other protein functions due to formation of 3-nitrotyrosine. Here, we demonstrate a role of selenium-containing enzymes catalyzing peroxynitrite reduction using glutathione peroxidase (GPx) as an example. GPx protected against the oxidation of dihydrorhodamine 123 by peroxynitrite more effectively than ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a selenoorganic compound exhibiting a high second-order rate constant for the reaction with peroxynitrite, 2 ؋ 10 6 M ؊1 s ؊1 . Carboxymethylation of selenocysteine in GPx by iodoacetate led to the loss of "classical" glutathione peroxidase activity but maintained protection against peroxynitrite-mediated oxidation. The maintenance of protection by GPx against peroxynitrite requires GSH as reductant.When peroxynitrite was infused to maintain a 0.2 M steady-state concentration, GPx in the presence of GSH, but neither GPx nor GSH alone, effectively inhibited the hydroxylation of benzoate by peroxynitrite. Under these steady-state conditions peroxynitrite did not cause the loss of classical GPx activity. GPx, like selenomethionine, protected against protein 3-nitrotyrosine formation in human fibroblast lysates, shown in Western blots. The formation of nitrite rather than nitrate from peroxynitrite was enhanced by GPx or by selenomethionine. The results demonstrate a novel function of GPx and potentially of other selenoproteins containing selenocysteine or selenomethionine, in the GSH-dependent maintenance of a defense line against peroxynitritemediated oxidations, as a peroxynitrite reductase.Peroxynitrite is a potent biological oxidant (1) generated, e.g. by endothelial cells, Kupffer cells, neutrophils, and macrophages (see Beckman (2) for review). Peroxynitrite (ONOO Ϫ ) is a relatively stable species compared with free radicals, but peroxynitrous acid (ONOOH) decays with a rate constant of 1.3 s Ϫ1

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Formation of thiocarbonyl compounds in the reaction of Ebselen oxide with thiols

Cited by 66 publications

References 0 publications

Sulfoxides as Urinary Metabolites ofS-Allyl-l-Cysteine in Rats: Evidence for the Involvement of Flavin-Containing Monooxygenases

Sulfoxides as Urinary Metabolites ofS-Allyl-l-Cysteine in Rats: Evidence for the Involvement of Flavin-Containing Monooxygenases

High-Throughput Screening Using the Differential Radial Capillary Action of Ligand Assay Identifies Ebselen As an Inhibitor of Diguanylate Cyclases

Glutathione Peroxidase Protects against Peroxynitrite-mediated Oxidations

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