Email Facebook Twitter Enzyme kinetics and substrate selectivities of rat glutathione S-transferase isoenzymes towards a series of new 2-substituted 1-chloro-4-nitrobenzenes 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 184.108.40.206; Isoenzymes Subject Nutritionglutathione transferaseisoenzymenitrobenzene derivativeanimal tissuearticlecontrolled studyenzyme kineticsenzyme specificityglutathione metabolismnonhumanratAnimalsChromatography, AffinityDinitrochlorobenzeneGlutathione TransferaseIsoenzymesKidneyKineticsLiverRatsSpectrophotometry, UltravioletSubstrate SpecificityAnimaliaFelis catus To reference this document use: http://resolver.tudelft.nl/uuid:7059d663-c604-4feb-884f-c76bc8b30d85 TNO identifier 233289 ISSN 0049-8254 Source Xenobiotica, 26 (2), 143-155 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.