Reactionestrone+reduced [NADPH--hemoprotein reductase]+dioxygen→4-hydroxyestrone+oxidized [NADPH--hemoprotein reductase]+water+hydronLeft to right · Balance undeterminableCatalystsCYP1A1CYP1A2CYP3A4CYP3A5CYP3A7CYP1B1Rhea RHEA:47292·2026-08-19·CC BY 4.0Reference data