title: Specific inactivation of glutathione S-transferases in class Pi by SH-modifiers.
abstract: Treatment of Class Pi glutathione S-transferases (GST) such as rat GST P (7-7), human GST pi and mouse GST MII with 0.05-0.1 mM N-ethylmaleimide (NEM) in 0.1 M Tris-HCl (pH 7.8) resulted in almost complete inactivation of these forms, whereas no or less inactivation occurred for GSTs in Class Alpha and Mu under the same conditions. Inactivated GST P lost its S-hexyl-GSH-Sepharose column affinity. About 0.8 mol of [14C]NEM was found to be covalently bound to 1 mol of GST P subunit when 80% of the activity was lost. Similar treatment with N-dimethyl-amino-3,5-dinitrophenyl maleimide, a colored analogue of NEM, followed by trypsin digestion, HPLC and amino acid sequence analysis revealed that one cysteine residue at the 47th position from the N-terminal of the GST P subunit was preferentially modified. Subunits of GST P and GST pi are known to have 4 cysteine residues at the same corresponding positions. The present results suggest that the 47th cysteine residue may be located in the vicinity of the active site of Class Pi GSTs.
authors.affiliation: Second Department of Biochemistry, Hirosaki University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tamai
authors.forename: K
authors.initials: K
authors.lastname: Satoh
authors.forename: S
authors.initials: S
authors.lastname: Tsuchida
authors.forename: I
authors.initials: I
authors.lastname: Hatayama
authors.forename: T
authors.initials: T
authors.lastname: Maki
authors.forename: K
authors.initials: K
authors.lastname: Sato
mesh_terms: D000818:Animals; D001665:Binding Sites; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005033:Ethylmaleimide / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors*; D008099:Liver / Q000201:enzymology*; D051379:Mice; D051381:Rats
chemical_list: D007527:Isoenzymes; D005982:Glutathione Transferase; D005033:Ethylmaleimide