title: The interactions of triethyltin with rat glutathione-S-transferases A, B and C. Enzyme-inhibition and equilibrium-dialysis studies.
abstract: Purified glutathione(GSH)-S-transferases A, B and C from rat liver are inhibited by triethyltin (SnEt3). With 1-chloro-2,4-dinitro benzene (CDNB) as the limiting substrate the inhibition is competitive in each case. At a GSH concentration of 5 . 10(-3) M the inhibition constants for transferases A and C at 25 degrees C are similar and very low, 3.2 . 10(-8) M and 5.6 . 10(-8) M respectively, whereas for transferase B the inhibition constant is 3.5 . 10(-5) M. Equilibrium-dialysis experiments carried out at 4 degrees C in the absence of GSH give apparent dissociation constants of 7.1 . 10(-4) M and 3.4 . 10(-4) M for transferases A and B respectively, but if 5 . 10(-3) M glutathione is included in the dialysis solutions these values fall to 2.0 . 10(-7) M and 2.6 . 10(-5) M, which are within an order of magnitude of the kinetic Ki-values. Chromatographic experiments with Sephadex G-10 show that GSH and SnEt3 interact in aqueous solution under the conditions of the enzyme-kinetic and equilibrium-dialysis experiments. It is suggested that the inhibited enzymes are in the form of ternary complexes, enzyme-GSH-SnEt3, in which GSH and SnEt3 may or may not interact directly; or are possibly quaternary complexes, enzyme-(GSH)2-SnEt3. SnEt3 could be valuable as a selective inhibitor of transferases A and C in mixtures of the three transferases.
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D003956:Dialysis; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D011485:Protein Binding; D051381:Rats; D014220:Trialkyltin Compounds / Q000494:pharmacology*; D014267:Triethyltin Compounds / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D014220:Trialkyltin Compounds; D014267:Triethyltin Compounds; D005982:Glutathione Transferase