52993-47-2Relevant academic research and scientific papers
Stereoselective Catalysis of a Retro-Michael Reaction by Class Mu Glutathione Transferases. Consequences for the Internal Distribution of Products in the Active Site
Chen, Jihong,Armstrong, Richard N.
, p. 580 - 585 (2007/10/03)
The reaction of glutathione (GSH) with trans-4-phenyl-3-buten-2-one (PBO) is readily reversible in aqueous solution with an apparent (pH-dependent) equilibrium constant at pH 8 of 6.4 x 1E2 M-1. Two class mu isoenzymes of GSH transferase from rat (M1-1 and M2-2) and two site specific mutants (M1-1/V9I and M2-2/I9V) catalyze the addition of GSH to PBO and the elimination of GSH from the two diastereomeric products (isomers A and B) of 4-(S-glutathionyl)-4-phenyl-2-butanone with varying degrees of efficiency and stereoselectivity, with the major kinetic product in the addition reaction (isomer A) being the preferred substrate for the elimination reaction. The kinetic stereoselectivity of the addition reaction and the steady-state kinetics of the elimination reactions with product isomers A and B are used to estimate internal stereochemical equilibrium constants in which product isomer B is predominant. This result is consistent with the internal equilibrium constants measured under conditions of enzyme in excess. The results can be used to construct reaction coordinate diagrams for the interconversion of central complexes in the enzyme-catalyzed reactions. The possible metabolic consequences of the reversibility of additions of GSH to α,β-unsaturated carbonyl compounds are discussed.
Redox Reactions of Thiol Free Radicals with the Antioxidants Ascorbate and Chlorpromazine: Role in Radioprotection
Tamba, Maurizio,O'Neill, Peter
, p. 1681 - 1685 (2007/10/02)
The interaction of the thiyl radical from glutathione, GS*, and its corresponding peroxyl radical adduct, GSO2*, with the reducing agents, ascorbate and chlorpromazine, have been studied in aqueous solution at pH 5.0-5.5 using the technique of pulse radiolysis with spectrophotometric detection.The rate constants determined for interaction of GS* with ascorbate and chlorpromazine are 5.4 * 108 and 9.0 * 108 dm3 mol-1 respectively.The reaction is thought to proceed via an electron transfer process.Further, the redox potential of GS*/GSH at pH 5.0 is estimated to be 0.91 V.In the presence of different concentrations of oxygen, it has been established that GSO2*, as observed at 540 nm, interacts with ascorbate and chloropromazine by electron transfer with rate constants of 2.1 * 108 and 5.0 * 108 dm3 mol-1 s-1 respectively.From these kinetic observations it is inferred that GSO2* is a weaker oxidant than GS*.From these findings the role of these glutathione radicals should be taken into account when considering the biological role of thiols in oxidative damage in biological systems.
Aminopyrine and Antipyrine Free Radical-cations: Pulse Radiolysis Studies of One-electron Transfer Reactions
Forni, Luigi G.,Mora-Arellano, Victor O.,Packer, John E.,Willson, Robin L.
, p. 1579 - 1584 (2007/10/02)
Absolute rate constants for the reaction of a variety of electrophilic free radicals with the pyrazoline derivatives aminopyrine and antipyrine have been measured by pulse radiolysis.In the case of aminopyrine the resulting radical cation is a particularly stable species ε325 5.35*103 dm3 mol-1 cm-1).Both compounds are readily oxidised to their respective radical-cations with the one-electron oxidation potential of antipyrine (E0 1.1-1.6 V) being higher than that of aminopyrine (E0 0.26-0.5 V).Studies of the reaction of the radical-cations with reducing agents suggest that aminopyrine in particular may prove to be a useful reference compound in studies of free radical one-electron oxidations.
