Title
Enzyme kinetics and substrate selectivities of rat glutathione S-transferase isoenzymes towards a series of new 2-substituted 1-chloro-4-nitrobenzenes
Author
van der Aar, E.M.
Buikema, D.
Commandeur, J.N.M.
te Koppele, J.M.
van Ommen, B.
van Bladeren, P.J.
Vermeulen, N.P.E.
Leiden/Amsterdam Ctr. for Drug Res., Department of Pharmacochemistry, Vrije Universiteit, De Boelelaan 1083, 1081 HV, Amsterdam, Netherlands TNO Preventie en Gezondheid TNO Voeding
Publication year
1996
Abstract
1. Four different rat glutathione S-transferase (GST) isoenzymes, belonging to three different classes, were examined for their GSH conjugating capacity towards 11 2-substituted 1-chloro-4-nitrobenzene derivatives. Significant differences were found in their enzyme kinetic parameters K(m), k(cat) and k(cat)/K(m). 2. Substrates with bulky substituents on the ortho-position appeared to have high affinities (low K(m)'s) for the active site of the GST-isoenzymes, suggesting that there is sufficient space in this area of the active site. A remarkably high K(m) (low affinity) was found for 2-chloro-5-nitropyridine towards all GST-isoenzymes examined. 3. GST 3-3 catalysed the reaction between GSH and the substrates most efficiently (high k(cat)) compared with the other GST-isoenzymes. Moreover, GST 3-3 showed clear substrate selectivities towards the substrates with a trifluoromethyl-, chlorine- and bromine-substituent. 1-Chloro-2,4-dinitrobenzene and 2-chloro-5-nitrobenzonitrile were most efficiently conjugated by all four GST-isoenzymes examined. 4. When the rate of the conjugation reactions was followed, a linear increase of formation of GS-conjugate could be seen for 2-chloro-5-nitrobenzonitrile during a much longer period of time than for 1-chloro-2,4-dinitrobenzene with all GST-isoenzymes examined. Therefore, it is suggested that 2-chloro-5-nitrobenzonitrile might be recommended as an alternative model substrate in GST-research. Chemicals/CAS: Dinitrochlorobenzene, 97-00-7; Glutathione Transferase, EC 2.5.1.18; Isoenzymes
Subject
Nutrition
glutathione transferase
isoenzyme
nitrobenzene derivative
animal tissue
article
controlled study
enzyme kinetics
enzyme specificity
glutathione metabolism
nonhuman
rat
Animals
Chromatography, Affinity
Dinitrochlorobenzene
Glutathione Transferase
Isoenzymes
Kidney
Kinetics
Liver
Rats
Spectrophotometry, Ultraviolet
Substrate Specificity
Animalia
Felis catus
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TNO identifier
233289
ISSN
0049-8254
Source
Xenobiotica, 26 (2), 143-155
Document type
article