Enzymatic activities were reconstituted in the presence of dilauroylphosphatidylcholine (50 mg/ml), by mixing each P450 enzyme with cytochrome b5 and cytochrome P450 oxido-reductase in 1:1:10 molar ratio. Reactions were carried out at 35° in Tris-Cl buffer pH 7.4 containing 10 mM MgCl2, 0.1 M KCl, and 1 mM NADPH. Organic soluble products were resolved by reversed phase HPLC and quantified by on-line β detection (60). Shown are average Kcat values ±SE (in min-1) calculated from time courses of product formation vs incubation time.