76726-99-3Relevant articles and documents
Determination of reduced cysteine in oenological cell wall fractions of saccharomyces cerevisiae
Tirelli, Antonio,Fracassetti, Daniela,De Noni, Ivano
body text, p. 4565 - 4570 (2011/07/09)
Compounds containing cysteine residues, such as glutathione, can affect the redox potential of must and wine by reduction of o-quinones and hydrogen peroxide. The oenological yeast cell wall fractions contain cysteine residues in their protein structure, and they could affect both oxidative and odor properties of wine. An analytical approach based on the derivatization of cysteinyl residues with p-benzoquinone followed by reversed-phase high-performance liquid chromatography separation was developed to quantify glutathione and free and protein cysteine in 16 Saccharomyces cerevisiae strains and 12 commercial samples of yeast mannoproteins, hulls, and lysates. The chemical modifications induced by the Maillard reaction following the industrial preparation of such fractions were evaluated as well. Lysates showed the highest protein cysteine content and high contents of glutathione and free cysteine. Mannoproteins showed an intense Maillard reaction (furosine >60 mg/100 g protein), and most of the samples were able to bind thiol compounds with a potentially detrimental effect toward the thiol-related odors in wine.
Covalent protein adducts of hydroquinone in tissues from rats: Identification and quantitation of sulfhydryl-bound forms
Boatman,English,Perry,Fiorica
, p. 853 - 860 (2007/10/03)
The Michael-type addition of sulfhydryl groups to benzoquinone (BQ) or substituted benzoquinones is proposed as the primary mechanism by which these electrophilic intermediates react with either cellular glutathione or protein sulfhydryls. This reaction constitutes a reductive alkylation with a substituted hydroquinone (HQ) derivative resulting from the addition. In the case of HQ, oxidative conversion of the parent material to BQ followed by conjugation with glutathione leads to metabolic activation, producing intermediates which are nephrotoxic as well as having other proposed biological activities. Chemically, BQ may react with more than 1 equiv of glutathione (or other sulfhydryl reagents) to produce HQ derivatives substituted with up to four sulfhydryl groups. Similarly, multiply substituted protein - S adducts of HQ were anticipated to occur in vivo following administration of this material. In the current studies, sulfhydryl-bound HQ protein adducts were detected and quantitated in protein isolated from rats using a modification of the alkaline permethylation procedure of Slaughter and Hanzlik [(1993)Anal. Biochem. 208, 288-295]. In particular, total protein - S adducts to HQ in kidney or blood reached a level of 420 or 80 pmol/mg of protein, respectively, 6 h following a single gavage dose of 100 mg/kg HQ. Measured half-lives of protein - S adducts in kidney and blood were 23.9 and 36.0 h, respectively. The applicability of protein - S adducts as a tissue dosimeter for HQ is discussed.
Ring addition of the α-amino group of glutathione increases the reactivity of benzoquinone thioethers
Alt, Carmen,Eyer, Peter
, p. 1223 - 1233 (2007/10/03)
2-(Glutathion-S-yl)-1,4-benzoquinone was found to be remarkably unstable in phosphate butter (pH 7.4) even in the absence of oxygen. Intramolecular addition of the α-amino group of the glutamate residue to the quinone ring yielded ultimately 2,3-(glutathion-N,S-yl)-1,4-benzoquinone and 2,6- (glutathion-N,S-yl)-1,4-benzoquinone in a 3:1 ratio along with 2-(glutathion- S-yl)-1,4-hydroquinone. Kinetic studies indicated that the cyclization reactions proceeded at a rate k1 of 0.093 min-1, while intermolecular reactions followed a second-order kinetics with a k2 of 94 M-1 min-1 (pH 7.4, 37 °C), resulting in multiple polymerization products. Both intramolecular amino adducts of 2-(glutathion-S-yl)-1;4-benzoquinone are prone to hydrolysis, leading to the insertion of an additional OH group in the ring. These S-substituted trihydroxybenzene derivatives are particularly susceptible to autoxidation. The model compound 6-(N-acetylcystein-S-yl)-2- hydroxy-1,4-hydroquinone was shown to form readily two atropoisomeric biphenyls upon autoxidation: 2,4'-bis(N-acetylcystein-S-yl)-2',3,3',4,6,6'- hexahydroxybiphenyl, indicating C-C coupling, presumably via semiquinone radical intermediates. Thus, the sequence of glutathione S-addition, followed by oxidation, N-addition, oxidation, an 1 hydrolysis, constitutes a novel and very effective activation pathway of quinones for eliciting oxidative stress. These data underline the fact that glutathione conjugates of autoxidizable aromatics are no obligatory stable end products of a detoxication reaction. The possible toxicological impacts of intra- and intermolecular addition reactions of quinoid thiol conjugates are discussed.
