Low and high Km forms of dinitrophenylglutathione-stimulated ATPase in bovine lens

Dinitrophenyl S-glutathione (Dnp-SG) ATPase which catalyses the hydrolysis of ATP in the presence of GSH-conjugates has been implicated previously in the transport of these conjugates. In the present studies we demonstrate that Dnp-SG ATPase is present in bovine lens epithelium and cortex. The specific activity per mg membrane protein was found to be 75-fold higher in the epithelium as compared to the cortex. No enzyme was detected in the nuclear region of the lens. Dnp-SG ATPase was purified from bovine lens epithelium and cortex using Dnp-SG-Sepharose 6MB affinity chromatography. The partially purified Dnp-SG ATPase had two distinct Km values, 120 microM and 1.0 mM. The antibodies raised against human erythrocyte Dnp-SG ATPase cross-reacted with the bovine lens epithelium Dnp-SG ATPase which was identified by Western blot as a band corresponding to an approximate M(r) value of 80,000 Da.