The glutathione S-transferases in selenium and vitamin E deficiency

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Abstract
Preliminary experiments confirmed the work of others showing that the total glutathione peroxidase (GSH-px) activity of rat liver supernatant fraction may be resolved into 2 peaks of activity (peak I and II) by gel filtration, and that peak I is the Se-containing enzyme and peak II is another peroxidase indistinguishable from glutathione-S-transferase (GST). In Se and vitamin E deficiency, the total activity of the GSH-px became very low, and the total activity of GST with 1-chloro-2,4-dinitrobenzene (CDNB) as substrate was enhanced. Study of the time course of these changes as deficiency progressed indicated that the stimulus for the rise in GST(CDNB) activity was the fall in GSH-px activity which preceded it. The peroxidase activity of GST resides only in the GST AA, B and B2 forms of the enzyme, which were shown to be respectively a homodimer of the Ya subunit and a heterodimer of the YaYc subunit. As vitamin E and Se deficiency progressed, the B2 and AA forms of the enzyme showed enhanced activity, which was interpreted as implying that the Yc subunit of the enzyme becomes enriched as a consequence of the withdrawal of Se from the animal''s diet. Densitometric measurements of the Yc and Ya subunits confirmed that the amount of the Yc subunit was nearly doubled in selenium deficiency, relative to the Ya subunit.