Tian G, Stuart J D, Moss M L, Domanico P L, Bramson H N, Patel I R, Kadwell S H, Overton L K, Kost T A, Mook R A
Department of Molecular Biochemistry, Glaxo Research Institute, Research Triangle Park, North Carolina 27709.
Biochemistry. 1994 Mar 1;33(8):2291-6. doi: 10.1021/bi00174a041.
17 beta-(N-tert-butylcarbamoyl)-4-aza-5 alpha-androstan-1-en-3-one (finasteride), which has been approved for treatment of benign prostatic hyperplasia, is shown here to be a slow time-dependent inhibitor of human steroid 5 alpha-reductase isozyme 1. This inhibition is characterized by an initial, fast step where the inhibitor binds to the enzyme followed by a slow step that leads to a final enzyme-inhibitor complex (EI*). No recovery of activity from this EI* complex was observed after dialysis for 3 days. The formation of EI* is diminished in the presence of a competitive, reversible inhibitor, indicating that the inhibition is active site-directed. At 37 degrees C and pH 7.0, the rate constant for the second, slow inhibition step, k3, is (1.40 +/- 0.04) x 10(-3) s-1 and the pseudo-bimolecular rate constant, k3/Ki, is (4.0 +/- 0.3) x 10(3) M-1 s-1. This latter rate constant is less than the value of 2.7 x 10(5) M-1 s-1 determined for the inhibition of 5 alpha-reductase 2 by finasteride [Faller, B., Farley, D., & Nick, H. (1993) Biochemistry 32, 5705-5710].(ABSTRACT TRUNCATED AT 250 WORDS)
