title: The major isozyme of rat cardiac glutathione transferases. Its correspondence to hepatic transferase X.
abstract: A major isozyme of rat heart glutathione transferase was purified to homogeneity by Sephadex G-200 gel filtration, ammonium sulfate precipitation, CM-cellulose chromatography and affinity chromatography on S-hexylglutathione-linked Sepharose 6B. The purified isozyme was a dimer with an apparent relative molecular mass of 50 000 composed of two Yb-size subunits (Mr = 26 500). The isozyme is immunologically related to rat liver glutathione transferase X and 3-3, especially closely to transferase X, and no immunological cross-reactivity with subunits 1 and 2 of hepatic glutathione transferases was observed. The isoelectric point (pI = 6.9) of the isozyme was identical with and the substrate specificity was very similar to transferase X. Thus, the cardiac near-neutral isozyme is considered to be identical to glutathione transferase X recognized in rat liver. The amount of this near-neutral isozyme estimated to be present in heart tissue is 70 micrograms/g. The isozyme has relatively high activities towards alpha, beta-unsaturated carbonyl compounds such as trans-4-phenyl-3-buten-2-one and trans-4-hydroxynon-2-enal. The latter is a cytotoxic product resulting from lipid peroxidation of polyunsaturated fatty acids, and the cardiac isozyme may play a physiologically significant role with glutathione conjugation of this compound. In addition to the near-neutral isozyme, acidic forms with isoelectric points of 4.9, 5.2 and 5.5 were partially purified; some of them are considered to consist of subunits immunologically related to transferase X.
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: U
authors.initials: U
authors.lastname: Milbert
authors.forename: F
authors.initials: F
authors.lastname: Oesch
authors.forename: H
authors.initials: H
authors.lastname: Sies
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005982:Glutathione Transferase / Q000145:classification / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D005779:Immunodiffusion; D007526:Isoelectric Point; D007527:Isoenzymes / Q000145:classification / Q000302:isolation & purification*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D005982:Glutathione Transferase