187878-81-5Relevant articles and documents
Modulation of homocysteine toxicity by S-nitrosothiol formation: A mechanistic approach
Morakinyo, Moshood K.,Strongin, Robert M.,Simoyi, Reuben H.
, p. 9894 - 9904 (2010)
The metabolic conversion of homocysteine (HCYSH) to homocysteine thiolactone (HTL) has been reported as the major cause of HCYSH pathogenesis. It was hypothesized that inhibition of the thiol group of HCYSH by S-nitrosation will prevent its metabolic conversion to HTL. The kinetics, reaction dynamics, and mechanism of reaction of HCYSH and nitrous acid to produce S-nitrosohomocysteine (HCYSNO) was studied in mildly to highly acidic pHs. Transnitrosation of this non-protein-forming amino acid by 5-nitrosoglutathione (GSNO) was also studied at physiological pH 7.4 in phosphate buffer. In both cases, HCYSNO formed quantitatively. Copper ions were found to play dual roles, catalyzing the rate of formation of HCYSNO as well as its rate of decomposition. In the presence of a transition-metal ions chelator, HCYSNO was very stable with a halflife of 198 h at pH 7.4. Nitrosation by nitrous acid occurred via the formation of more powerful nitrosating agents, nitrosonium cation (NO +) and dinitrogen trioxide (N2O3). In highly acidic environments, NO+ was found to be the most effective nitrosating agent with a first-order dependence on nitrous acid. N 2O3 was the most relevant nitrosating agent in a mildly acidic environment with a second-order dependence on nitrous acid. The bimolecular rate constants for the direct reactions of HCYSH and nitrous acid, N2O3, and NO+were 9.0 × 10-2, 9.50 × 103, and 6.57 × 1010 M-1 s-1, respectively. These rate constant values agreed with the electrophilic order of these nitrosating agents: HNO2 2O3 +. Transnitrosation of HCYSH by GSNO produced HCYSNO and other products including glutathione (reduced and oxidized) and homocysteineglutathione mixed disulfide. A computer modeling involving eight reactions gave a good fit to the observed formation kinetics of HCYSNO. This study has shown that it is possible to modulate homocysteine toxicity by preventing its conversion to a more toxic HTL by S-nitrosation.
Mechanism-based triarylphosphine-ester probes for capture of endogenous RSNOs
Seneviratne, Uthpala,Godoy, Luiz C.,Wishnok, John S.,Wogan, Gerald N.,Tannenbaum, Steven R.
supporting information, p. 7693 - 7704 (2013/07/11)
Nitrosothiols (RSNOs) have been proposed as important intermediates in nitric oxide (NO?) metabolism, storage, and transport as well as mediators in numerous NO-signaling pathways. RSNO levels are finely regulated, and dysregulation is associated with the etiology of several pathologies. Current methods for RSNO quantification depend on indirect assays that limit their overall specificity and reliability. Recent developments of phosphine-based chemical probes constitute a promising approach for the direct detection of RSNOs. We report here results from a detailed mechanistic and kinetic study for trapping RSNOs by three distinct phosphine probes, including structural identification of novel intermediates and stability studies under physiological conditions. We further show that a triarylphosphine-thiophenyl ester can be used in the absolute quantification of endogenous GSNO in several cancer cell lines, while retaining the elements of the SNO functional group, using an LC-MS-based assay. Finally, we demonstrate that a common product ion (m/z = 309.0), derived from phosphine-RSNO adducts, can be used for the detection of other low-molecular weight nitrosothiols (LMW-RSNOs) in biological samples. Collectively, these findings establish a platform for the phosphine ligation-based, specific and direct detection of RSNOs in biological samples, a powerful tool for expanding the knowledge of the biology and chemistry of NO?-mediated phenomena.
Capillary zone electrophoretic detection of biological thiols and their S-nitrosated derivatives
Stamler, Jonathan S.,Loscalzo, Joseph
, p. 779 - 785 (2007/10/02)
Reduced thiols (RSH) react with certain oxides of nitrogen to yield S-nitroso thiols (RSNO) possessing smooth muscle relaxant and platelet inhibitory properties. Nitrosated derivatives of the biological thiols - glutathione, cysteine, and homocysteine - have therefore been considered as bioactive intermediates in the metabolism of organic nitrates and the endothelium-derived relaxing factor with properties of nitric oxide. As yet, however, there is no established chemical method for identifying the biological S-nitroso thiols and, consequently, litttle is known of their distinguishing chemical characteristics or biochemistry. In this study, we demonstrate for the first time a simple, rapid, and reproducible method for separating these thiols from their S-nitrosated derivatives using capillary zone electrophoresis. Cysteine, homocysteine, and glutathione were separated from one another and from their corresponding disulfides in 0.01 M phosphate buffer, pH 2.5, by capillary zone electrophoresis and absorbance detection at 200 nm with measured elution times of 5.92-16.15 min; corresponding S-nitroso thiols were selectively detected at 320 nm and eluted at 2.50-18.20 min. These data support the specificity and reproducibility of this technique for separation and identification of thiols, disulfides, and S-nitroso thiol derivatives.
