Distribution, induction and purification of a monooxygenase catalyzing sulphoxidation of drugs

Abstract

The enzyme, a monooxygenase, catalyzing the sulphoxidation of ethionamide (2-ethyl thioisonicotinamide) to ethionamide sulphoxide is located primarily in the liver and serum of guinea pigs. Administration of ethionamide enhances the activity of the enzyme; the enhancement in activity is due to increased synthesis of the enzyme. This oxygenase is not specific to ethionamide because compounds like chlorpromazine and thioridazine are also oxidized by the enzyme. However, administration of chlorpromazine itself does not induce the enzyme. The enzymes in various tissues (liver, pancreas, spleen, kidney and lungs) and serum of guinea pigs have been purified to homogeneity, as evidenced by electrophoretic and antigenic criteria. The comparison of properties of all these enzyme preparations reveals that the enzymes are identical. There is no apparent involvement of cytochrome P-450 in the sulphoxidation reaction.