Characterization of microsomal aniline hydroxylase of rainbow trout, Salmo gairdneri

Aniline hydroxylase from liver microsomes of rainbow trout Salmo gairdneri converted aniline to p-aminophenol, the specific activity being 0.068 nmoles/min/mg protein in potassium phosphate buffer, pH 7.4 at 25 degrees C. The maximal rate of the enzyme reaction was found at aniline concentrations above 5 mM and in the presence of NADPH. Vmax and K(m) were 0.048 nmoles/min/mg and 0.105 mM respectively. The Hill plot showed the Hill constant to be 1.02 indicating one substrate binding site with no cooperativity. Ca2+ and Mg2+ at concentrations ranging between 1-10 mM stimulated the enzyme activity.