A comparison of the leukotriene synthesizing ability of subfractions of rat liver glutathione s-transferases

Abstract

The cytosolic glutathione S-transferases of rat liver have been partially purified by affinity adsorption to glutathionyl Sepharose and elution with glutathione, and have been fractionated by chromatofocusing. The column eluates were pooled into ten fractions, although evaluation of the enzymatic activities of the column eluates with different chromogenic substrates indicated that some of the fractions were heterogeneous. The pooled fractions were characterized with respect to their substrate specificity, their susceptibility to inhibition by several inhibitors, and their ability to catalyze the conjugation of glutathione to leukotriene A 4. It was found that all the fractions were able to catalyze leukotriene C formation. The fraction having the highest specific activity with three different chromogenic substrates also had the highest specific activity when LTA was used as the substrate while, in general, there were marked differences in the relative activities of the different pooled fractions. The most active fraction represented approximately 50% of the total glutathione S-transferase activity in the whole preparation and had an apparent isoelectric point of 9.05. There was no apparent relationship between the ability of the different fractions to utilize LTA and any of the other substrates which were tested.