Interrelationship between anionic and cationic forms of glutathione S-transferases of human liver

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Abstract
Human liver glutathione S-transferases (GSH S-transferases) were fractionated into cationic and anionic proteins. During fractionation with (NH4)2SO4 the anionic GSH S-transferases are concentrated in the 65%-saturated-(NH4)2SO4 fraction, whereas the cationic GSH S-transferases separate in the 80%-saturated-(NH4)2SO fraction. From the 65%-saturated-(NH4)2SO4 fraction 2 new anionic GSH S-transferases, .omega. and .psi., were purified to homogeneity by using ion-exchange chromatography on DEAE-cellulose, Sephadex G-200 gel filtration, affinity chromatography on GSH bound to epoxy-activated Sepharose and isoelectric focusing. By a similar procedure, cationic GSH S-transferases were purified from the 80%-saturated-(NH4)2SO4 fraction. Isoelectric points of GSH S-transferases .omega. and .psi. are 4.6 and 5.4, respectivley. GSH S-transferase .omega. is the major anionic GSH S-transferase of human liver, whereas GSH S-transferase .psi. is present only in traces. The subunit MW of GSH S-transferase .omega. is about 22,500, whereas that of cationic GSH S-transferase is about 24,500. Kinetic and structural properties as well as the amino acid composition of GSH S-transferase .omega. are described. The antibodies raised against cationic GSH S-transferases cross-react with GSH S-transferase .omega.. There are significant differences between the catalytic properties of GSH S-transferase .omega. and the cationic GSH S-transferases. GSH peroxidase II activity is displayed by all 5 cationic GSH S-transferases, whereas both anionic GSH S-transferases do not display this activity.