On the multiplicity of rat liver glutathione S-transferases

Rat liver glutathione S-transferases have been purified to apparent electrophoretic homogeneity by S-hexylglutathione-linked Sepharose 6B affinity chromatography and CM-cellulose column chromatography. At least 11 transferase activity peaks can be resolved including five Yb size homodimeric isozymes, two Yc size homodimeric isozymes, one Ya homodimeric isozyme, one Y alpha homodimeric isozyme, and two Ya-Yc heterodimeric isozymes. Distribution of the GSH peroxidase activity among the CM-cellulose column fractions suggests the existence of further multiplicity in this isozyme family. Substrate specificity patterns of the Yb subunit isozymes revealed a possibility that each of the five Yb-containing isozymes is composed of a different homodimeric Yb size subunit composition. Our findings on the increasing multiplicity of glutathione S-transferase isozymes are consistent with the notion that multiple isozymes of overlapping substrate specificities are required to detoxify a multitude of xenobiotics in addition to serving other important physiological functions.