Abstract
Not only cytochrome P-450 and cytochrome P-450 reductase, but considerable amount of cytochrome b5 and cytochrome b5 reductase were also contained in the adrenal microsomes of guinea pig. Addition of nicotineamide adenine dinucleotide (NADH) stimulates the activities of cytochrome P-450 monooxygenases such as 21-hydroxylase, 17α-hydroxylase and C17, 20 lyase supported with nicotineamide adenine dinucleotide phosphate (NADPH) as a cofactor. In addition, substrate for Δ5-3β-hydroxysteroid dehydrogenase plus NAD+ also stimulate the same cytochrome P-450 monooxygenase activities. These observations were suggesting the participation of cytochrome b5 electron transport system on cytochrome P-450, monooxygenase (21 -hydroxylase, 17 α-hydroxylase and C17, 20 lyase) reactions associated with the biosynthesis of corticoids and adrenal androgens. Furthermore, it is also suggesting that cytochrome b5 electron transport system involves the reaction of Δ5-3β-hydroxysteroid dehydrogenase.
