The reduction of glutathione by plant tissues

Abstract

Extracts from ungerminated pea seeds under anaerobic conditions rapidly reduce glutathione (GSH). When these extracts are dialyzed there is a progressive fall in the activity of the extract. There is chromato-graphic evidence that both isocitric and malic acids are present in pea seeds. The activity of these dialyzed extracts may be restored by the addition of isocitrate or malate, coenzyme II (CoII) and Mn. With isocitrate, alpha-ketoglutaric acid and with malate, pyruvic acid is formed in amts. equivalent to the glutathione reduced. Coenzyme II cannot be replaced by coenzyme I. Reduced coenzyme II does not reduce glutathione in soln. in the absence of enzymic catalysts. Dialyzed pea extracts contain an enzyme which actively catalyzes the reaction Reduced CoII + GSSG CoII + 2GSH. The reduction of glutathione is equivalent to the amt. of coenzyme II oxidized. The reverse reaction between coenzyme II and reduced glutathione could not be demonstrated, indicating that the equilibrium is in favor of the formation of reduced glutathione. The presence in the dialyzed pea extracts of ethanol and formic dehydrogenase enzymes, both coenzyme I specific, was shown. These enzymes in the presence of their substrates and coenzyme I will not reduce glutathione; reduced coenzyme I will not reduce glutathione, nor was any evidence obtained of the presence of an enzyme which would catalyze the reaction. Dehydroascorbic acid is rapidly reduced to ascorbic acid when it is added to a dialyzed enzyme extract containing isocitrate, coenzyme n, and Mn glutathione. The reduction of dehydro- ascorbic acid is dependent on the production of reduced glutathione. When dehydroascorbic acid reductase is present, a system is complete by which H may be transferred in turn from the H of substrates of enzymes reducing coenzyme II to glutathione and dehydroascorbic acid.