1.14.14.99 cytochrome P-450 a heme-thiolate protein (P-450) 1.14.14.99 cytochrome P450 - 1.14.14.99 cytochrome P450 heme-thiolate protein, 0.2-0.9 nmol per mg protein 1.14.14.99 NADPH-hemoprotein reductase A flavoprotein containing both FMN and FAD. This enzyme catalyses the transfer of electrons from NADPH, an obligatory two-electron donor, to microsomal P-450 monooxygenases, EC 1.14.14._