Interrelationship between cationic and anionic forms of glutathione S-transferases of bovine ocular lens

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Abstract
Since the eye is constantly exposed to potentially damaging chemical compounds present in the atmosphere and vascular system, the physiological role of glutathione S-transferase (GSH S-transferase) in detoxification mechanisms operative in the ocular lens was studied. An anionic and a cationic GSH S-transferase from the bovine lens were purified to homogeneity through a combination of gel filtration, ion-exchange and affinity chromatography. The anionic (pI 5.6) and cationic (pI 7.4) S-transferases had distinct kinetic parameters (apparent Km and Vmax pH optimum and energy of activation). Both species had similar MW and amino acid compositions. Double-immunodiffusion and immunotitration revealed both lens S-transferases were immunologically similar. The very close similarity in amino acid compositions and immunological properties strongly indicates that these 2 transferases originate from the same gene or at least share common antigenic determinants and originate from similar genes. The bovine lens GSH S-transferases had no glutathione peroxidase activity with t-butyl hydroperoxide or cumene hydroperoxide as substrate. The antibody raised against the homogeneous anionic glutathione S-transferase from the bovine lens precipitated glutathione S-transferase and glutathione peroxidase activities out of solution in the supernatant of a crude bovine liver homogenate.