Characteristics of the microsomal N-hydroxylation of benzamidine to benzamidoxime

Abstract

1. A simple and fast h.p.l.c. analysis of benzamidoxime formed by microsomal N-hydroxylation of benzamidine is presented which is well suited for the determination of the N-oxygenation activity of microsomal enzymes.

2. Optimal reaction conditions were determined. The apparent K_m and V_max values were, respectively, 1–61 mM and 0.38nmol benzamidoxime/min per mg protein.

3. The effects of the inducers phenobarbital, 3-methylcholanthrene and benzamidine itself on hepatic benzamidine metabolizing activity in rabbits were determined.

4. Neither superoxide anion nor hydrogen peroxide is directly involved in the N-hydroxylation reaction.

5. The direct involvement of cytochrome P-450 in the N-hydroxylation of benzamidine is supported by the observation that inhibitors of cytochrome P-450, in particular carbon monoxide, markedly decreased the rate of N-oxygenation.