Purification and biochemical characterization of cytosolic glutathione-S-transferase from malarial parasites Plasmodium yoelii.

Glutathione (GSH) metabolism represents a potential target for antiparasitic drug design. Glutathione-S-transferase (GST), an important enzyme of the GSH cycle, is considered to be an essential detoxification enzyme in parasitic species. Soluble GST from rodent malarial parasites Plasmodium yoelii was purified to homogeneity using a combination of salt precipitation, affinity chromatography on GSH-sepharose 6B and ultrafiltration. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed a single band and activity staining was also detected on PAGE gels. Kinetic studies on the purified enzyme revealed significant differences between the parasitic and mammalian enzymes. The purified enzyme exhibited an optimum pH of 8.2 and K (m) values of 0.2+/-0.213 and 3.3+/-0.056 mM with respect to co-substrate GSH and substrate 1-chloro-2, 4-dinitrobenzene (CDNB), respectively. Hemin, the known mammalian GST inhibitor was found to be a potent inhibitor of P. yoelii GST, with a K (i) of 4.0 microM.