Irreversible inhibition of rat glutathione S-transferase 1-1 by quinones and their glutathione conjugates. Structure-activity relationship and mechanism. 1991

B van Ommen, and J H Ploemen, and J J Bogaards, and T J Monks, and S S Gau, and P J van Bladeren
TNO Toxicology and Nutrition Institute, Department of Biological Toxicology, Zeist, The Netherlands.

The irreversible inhibition of the rat glutathione S-transferase (GST) isoenzyme 1-1 by a series of halogenated 1,4-benzoquinones and their GSH conjugates was studied quantitatively by analysing the time course of enzyme inactivation. With increasing numbers of chlorine substituents, the rate of inhibition greatly increased. Incorporation of a GSH moiety in all cases increased the rate of inactivation compared with the non-substituted compound, and this was due to the increased affinity of the inhibitor for the active site. The ratio between the rates of inhibition for a given quinone with and without GSH substituent was largest for the three dichlorobenzoquinones, with the 2,6-isomer showing a 41-fold increase in rate of inhibition upon conjugation with GSH. The time courses of inhibition could be fitted either to a bi-exponential function (for the GSH conjugates and the higher chlorinated quinones) or to a mono-exponential function (all other quinones). It is concluded that the second component describes the affinity part of the reaction. GST 1-1 possesses two cysteine residues, with modification of one of these, probably located in the vicinity of the active site, having a major impact on the enzyme activity. Compounds with affinity towards the active site preferentially react with this residue. Non-specific quinones react equally with both cysteine residues. This was confirmed by the observation that complete inactivation of GST 1-1 by 2,5-dichlorobenzoquinone was achieved only after modification of two residues, whereas the corresponding GSH conjugate already completely inhibited the enzyme after modification of one residue.

UI MeSH Term Description Entries
D007527 Isoenzymes Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics. Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D011809 Quinones Hydrocarbon rings which contain two ketone moieties in any position. They can be substituted in any position except at the ketone groups.
D003545 Cysteine A thiol-containing non-essential amino acid that is oxidized to form CYSTINE. Cysteine Hydrochloride,Half-Cystine,L-Cysteine,Zinc Cysteinate,Half Cystine,L Cysteine
D004789 Enzyme Activation Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D005978 Glutathione A tripeptide with many roles in cells. It conjugates to drugs to make them more soluble for excretion, is a cofactor for some enzymes, is involved in protein disulfide bond rearrangement and reduces peroxides. Reduced Glutathione,gamma-L-Glu-L-Cys-Gly,gamma-L-Glutamyl-L-Cysteinylglycine,Glutathione, Reduced,gamma L Glu L Cys Gly,gamma L Glutamyl L Cysteinylglycine
D005982 Glutathione Transferase A transferase that catalyzes the addition of aliphatic, aromatic, or heterocyclic FREE RADICALS as well as EPOXIDES and arene oxides to GLUTATHIONE. Addition takes place at the SULFUR. It also catalyzes the reduction of polyol nitrate by glutathione to polyol and nitrite. Glutathione S-Alkyltransferase,Glutathione S-Aryltransferase,Glutathione S-Epoxidetransferase,Ligandins,S-Hydroxyalkyl Glutathione Lyase,Glutathione Organic Nitrate Ester Reductase,Glutathione S-Transferase,Glutathione S-Transferase 3,Glutathione S-Transferase A,Glutathione S-Transferase B,Glutathione S-Transferase C,Glutathione S-Transferase III,Glutathione S-Transferase P,Glutathione Transferase E,Glutathione Transferase mu,Glutathione Transferases,Heme Transfer Protein,Ligandin,Yb-Glutathione-S-Transferase,Glutathione Lyase, S-Hydroxyalkyl,Glutathione S Alkyltransferase,Glutathione S Aryltransferase,Glutathione S Epoxidetransferase,Glutathione S Transferase,Glutathione S Transferase 3,Glutathione S Transferase A,Glutathione S Transferase B,Glutathione S Transferase C,Glutathione S Transferase III,Glutathione S Transferase P,Lyase, S-Hydroxyalkyl Glutathione,P, Glutathione S-Transferase,Protein, Heme Transfer,S Hydroxyalkyl Glutathione Lyase,S-Alkyltransferase, Glutathione,S-Aryltransferase, Glutathione,S-Epoxidetransferase, Glutathione,S-Transferase 3, Glutathione,S-Transferase A, Glutathione,S-Transferase B, Glutathione,S-Transferase C, Glutathione,S-Transferase III, Glutathione,S-Transferase P, Glutathione,S-Transferase, Glutathione,Transfer Protein, Heme,Transferase E, Glutathione,Transferase mu, Glutathione,Transferase, Glutathione,Transferases, Glutathione
D006219 Halogens A family of nonmetallic, generally electronegative, elements that form group 17 (formerly group VIIa) of the periodic table. Halogen,Group 17 Elements,Elements, Group 17
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D013237 Stereoisomerism The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed) Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer

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