Purification and characterization of three forms of glutathione S-transferase A. A comparative study of the major YaYa-, YbYb- and YcYc-containing glutathione S-transferases

Abstract

Rat liver glutathione S-transferases have previously been defined by their elution behaviour from DEAE-cellulose and CM-cellulose as M, E, D, C, B, A and AA. These enzymes are dimeric proteins which comprise subunits of mol.wt. 22 000 (Ya), 23 500 (Yb) or 25 000 (Yc). Evidence is presented that YaYa protein, one of two previously described lithocholate-binding proteins which exhibit transferase activity, is an additional enzyme which is not included in the M, E, D, C, B, A and AA nomenclature. We therefore propose that this enzyme is designated transferase YaYa. Transferases YaYa, C, A and AA have molecular weights of 44 000, 47 000, 47 000 and 50 000 respectively and each comprises two subunits of identical size. These enzymes were purified to allow a study of their structural and functional relationships. In addition, transferase A was further resolved into three forms (A1, A2 and A3) which possess identical activities and structures and appear to be the product of a single gene. Transferases YaYa, C, A and AA each had distinct enzymic properties and were inhibited by cholate. The recently proposed proteolytic model, which attributes the presence of multiple forms of glutathione S-transferase activity to partial proteolysis of transferase AA, was tested and shown to be highly improbable. Peptide maps showed significant differences between transferases YaYa, C, A and AA. Immunotitration studies demonstrated that antisera raised against transferases YaYa and C did not precipitate transferase AA.

Evidence that human class Theta glutathione S-transferase T1-1 can catalyse the activation of dichloromethane, a liver and lung carcinogen in the mouse: Comparison of the tissue distribution of GST T1-1 with that of classes Alpha, Mu and Pi GST in human

“…GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB) and glutathione peroxidase activity with cumene hydroperoxide were measured at 340 nm with the Cobas Fara II Chemistry System (Hoffmann-La Roche Ltd, Basel, Switzerland) [32,33]. In all enzyme activity assays, the non-enzymic reaction rate was measured and subtracted from the overall reaction rate.…”

Expression and Inducibility of Alpha, Pi, and Mu Glutathione S-Transferase Protein and mRNA in Murine Lung

“…On the basis of decreasing electrophoretic mobilities, three pro-tein bands were resolved and were designated Ya, Yb, and Yc (17). Subsequent studies showed that the Ya and Yc bands represent class alpha GST, whereas the Yb band represents class mu GST (18,19). These findings were used to devise a class-based nomenclature for GST subunits (20).…”

Sex-specific constitutive expression of the pre-neoplastic marker glutathione S-transferase, YfYf, in mouse liver

“…245 Abbreviations used: GST, glutathione S-transferase; CDNB, I-chloro-2,4-dinitrobenzene; DCNB, 1,2-dichloro-4-nitrobenzene; PAGE, polyacrylamide-gel electrophoresis. Hayes & Clarkson (1982). Assays for microsomal GST, with CDNB as substrate, were performed manually as described by Morgenstern et al (1980).…”