ABSTRACT
The kinetics of 2-aminofluorene [AF] and 4-Aminobiphenyl [4-AB] N-hydroxylase reactions were determined using eight highly purified forms of rabbit liver cytochrome-P450 [Cyt-P450], with control and 2,3,7,8-tetrchloro-dibenzo-p-dioxin [TCDD] induced rabbit lung and liver microsomes.Both AF and 4-AB N-hydroxylases were best defined by two enzymatic systems, showing a high affinity and low capacity and a low affinity; high capacity system in control and TCDD pretreated microsomes. TCDD pretreatment differently modifies the apparent Km and Vmax. of the arylmine N-hydroxylases in the two tissues microsomal enzymes and in a substrate-dependent manner. Cyt-P450 [form 4] showed the following AF N-hydroxylase activity: 3417 +/- 326 pmol N-OH-AF/nmol Cyt-450/min. In contrast to the microsomal situation, the kinetics studies of AF and 4-AB N-hydroxylases with the form 4, were best described by one enzymatic system.