Identification of a basic hybrid glutathione S-transferase from human liver. Glutathione S-transferase δ is composed of two distinct subunits (B1 and B2)

Abstract

The purification of a hybrid glutathione S-transferase (B1B2) from human liver was described. This enzyme has an isoelectric point [pI] of 8.75 and the B1 and B2 subunits are distinguishable immunologically and are ionically distinct. Hybridization experiments demonstrated that B1B1 and B2B2 could be resolved by CM-cellulose chromatography and have pI values of 8.9 and 8.4, respectively. Transferase B1B2 and the 2 homodimers from which it is formed, are electrophoretically and immunochemically distinct from the neutral enzyme (transferase .mu.) and 2 acidic enzymes (transferases .pi. and .lambda.). Sodium dodecyl sulfate/polyacrylamide-gel electrophoresis demonstrated that B1 and B2 both have an MW of 26,000; in contrast, transferase .mu. comprises subunits of MW 27,000 and transferases .pi. and .lambda. both comprise subunits of MW 24,500. Antisera raised against B1 or B2 monomers did not cross-react with the neutral or acidic glutathione S-transferases. The identity of transferase B1B2 with glutathione S-transferase .delta. prepared by the method of Kamisaka, Habig, Ketley, Arias and Jakoby was demonstrated, as well as its relationship to other previously described transferases.