Selective elution of rodent glutathione S-transferases and glyoxalase I from the S-hexyglutathione-Sepharose affinity matrix

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Abstract
1. The major hepatic glutathione S-transferases (GSTs) from gerbil, guinea-pig, hamster, mouse and rat comprise Ya- (Mr 25,500-25,800), Yb- (Mr 26,100-26,400), Yc- (Mr 27,000-27,500) and Yf- (Mr 24,800) type subunits. 2. In all rodent species the GST subunits possess characteristic affinities for S-hexylglutathione-Sepharose and are eluted at distinct positions when a gradient of counter-ligand is employed to develop this affinity gel. The enzymes that bind to this matrix can be eluted, according to their subunit composition, in the order Ya-, Yc-, Yf- and Yb-containing GST; glyoxalase I, also retained by S-hexylglutathione-Sepharose, is eluted after the major GST YbYb peak. 3. Conditions are also described for the isocratic affinity elution of S-hexylglutathione-Sepharose that allow rat GST to be divided into four separate fractions (pools 1-4). A further fraction (pool 5) can be prepared from material that does not bind S-hexylglutathione-Sepharose and is obtained by chromatography on glutathione-Sepharose. 4. The sequential use of S-hexylglutathione-Sepharose and glutathione-Sephaose has facilitated the isolation of novel GSTs by enriching the various affinity-purified fractions with different subunits. This strategy allowed the Yk (Mr 25,000) and Yo (Mr 26,500) subunits from rat testis as well as Yl (M4 25,700) from rat kidney to be rapidly purified. 5. The binding properties of GST subunits for S-hexylglutathione-Sepharose have been compared with their Km values for GSH. The elution order from this matrix is inversely related to the Km value. The GSTs that do not bind to S-hexylglutathione-Sepharose have considerably higher Km values for GSH (i.e. > 2.0 mM) than do those enzymes that readily bind to the affinity gel (i.e. 0.13-0.77 mM). GST YkYk and YoYo, which have weak affinities for S-hexylglutathione-Sepharose, possess intermediate Km values for GSH of 1.0 and 1.2 mM respectively.

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