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Purification and properties of anionic glutathione S-transferase from bovine ciliary body.

ABSTRACT: An anionic glutathione S-transferase was purified from bovine ciliary body by DEAE-agarose chromatography and affinity chromatography on GSH-agarose and Orange A. The enzyme accounts for about 25% of total soluble glutathione S-transferase activity of the tissue. The purified enzyme has a molecular mass of about 50,000 Da and is composed of two identical subunits of about 25,000 Da. The enzyme has a pI of 5.8. The enzyme conjugates GSH with 1-chloro-2,4-dinitrobenzene, p-nitrobenzyl chloride, 1,2-epoxy-3-(p-nitrophenyl)propane, 1,2-dinitrobenzene and 3,4-dinitrobenzoic acid. The Km values for 1-chloro-2,4-dinitrobenzene and GSH are 0.40 mM and 0.57 mM respectively. Haematin is a non-competitive inhibitor (Ki = 4.5 microM) when tested with various concentrations of 1-chloro-2,4-dinitrobenzene. The enzyme shows no glutathione peroxidase activity with either H2O2 or cumene peroxide as substrate. On the basis of substrate specificities, pI values, amino acid composition and peptide maps, it is concluded that the ciliary-body enzyme is probably identical with the anionic form of glutathione S-transferase from bovine lens and liver.

SUBMITTER: Shichi H

PROVIDER: S-EPMC1146995 | biostudies-other | 1986 Jul

REPOSITORIES: biostudies-other

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Project description:A hitherto unknown cytosolic glutathione S-transferase from rat liver was discovered and a method developed for its purification to apparent homogeneity. This enzyme had several properties that distinguished it from other glutathione S-transferases, and it was named glutathione S-transferase X. The purification procedure involved DEAE-cellulose chromatography, (NH4)2SO4 precipitation, affinity chromatography on Sepharose 4B to which glutathione was coupled and CM-cellulose chromatography, and allowed the isolation of glutathione S-transferases X, A, B and C in relatively large quantities suitable for the investigation of the toxicological role of these enzymes. Like glutathione S-transferase M, but unlike glutathione S-transferases AA, A, B, C, D and E, glutathione S-transferase X was retained on DEAE-cellulose. The end product, which was purified from rat liver 20 000 g supernatant about 50-fold, as determined with 1-chloro-2,4-dinitrobenzene as substrate and about 90-fold with the 1,2-dichloro-4-nitrobenzene as substrate, was judged to be homogeneous by several criteria, including sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, isoelectric focusing and immunoelectrophoresis. Results from sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and gel filtration indicated that transferase X was a dimer with Mr about 45 000 composed of subunits with Mr 23 500. The isoelectric point of glutathione S-transferase X was 6.9, which is different from those of most of the other glutathione S-transferases (AA, A, B and C). The amino acid composition of transferase X was similar to that of transferase C. Immunoelectrophoresis of glutathione S-transferases A, C and X and precipitation of various combinations of these antigens by antisera raised against glutathione S-transferase X or C revealed that the glutathione S-transferases A, C and X have different electrophoretic mobilities, and indicated that transferase X is immunologically similar to transferase C, less similar to transferase A and not cross-reactive to transferases B and E. In contrast with transferases B and AA, glutathione S-transferase X did not bind cholic acid, which, together with the determination of the Mr, shows that it does not possess subunits Ya or Yc. Glutathione S-transferase X did not catalyse the reaction of menaphthyl sulphate with glutathione, and was in this respect dissimilar to glutathione S-transferase M; however, it conjugated 1,2-dichloro-4-nitrobenzene very rapidly, in contrast with transferases AA, B, D and E, which were nearly inactive towards that substrate.(ABSTRACT TRUNCATED AT 400 WORDS)

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Purification and properties of anionic glutathione S-transferase from bovine ciliary body.

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