Inhibition of Human Steroid 5β-Reductase (AKR1D1) by Finasteride and Structure of the Enzyme-Inhibitor Complex

The study investigated the inhibition of human steroid 5β-reductase (AKR1D1) by finasteride and the structure of the enzyme-inhibitor complex. Finasteride was found to be a competitive inhibitor of AKR1D1 with low micromolar affinity. The crystal structure of the AKR1D1-NADP+ finasteride complex showed that finasteride binds perpendicular to the NADP+ cofactor and is rotated by ~12° with respect to progesterone. The study provides insight into the mechanism of action of finasteride, which is used to treat hair loss and prostate enlargement.