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Biochemistry. 1995 Oct 17;34(41):13453-9.

Mechanism of time-dependent inhibition of 5 alpha-reductases by delta 1-4-azasteroids: toward perfection of rates of time-dependent inhibition by using ligand-binding energies.

Author information

1
Division of Biochemistry, Glaxo Wellcome Research Institute, Research Triangle Park, North Carolina 27709, USA.

Abstract

Finasteride (17 beta-N-tert-butylcarbamoyl-4-aza-5 alpha-androstan-1-en-3- one) is a time-dependent, apparently irreversible inhibitor of 5 alpha-reductases, but does not fully inhibit the activity of 5 alpha-reductase in vivo. This limited efficacy has been attributed to its slow rate of inhibition against the type-1 isozyme [Tian, G. (1995) J. Pharm. Sci. (in press)]. Here the feasibility of increasing the rate of inhibition of 5 alpha-reductases by providing binding energies with the inhibitor at a site remote from the center of chemical transformation was explored. Substitution of N-(2,5-bis(trifluoromethyl)phenyl) group, which had been shown to benefit 6-azasteroids in the binding to 5 alpha-reductases [Frye, S., Haffner, C. D., Maloney, P. R., Hiner, R. N., Unwalla, R. J., Batchelor, K. W., Bramson, H. N., Stuart, J. D., Schweiker, S. L., Van Arnold, J., Bickett, D. M., Moss, M. L., Tian, G., Lee, F. W., Tippin, T. K., James, M. K., Grizzle, M. K., Long, J. E., & Croom, D. K. (1995) J. Med. Chem. 38, 2621-2627], for the N-tert-butyl substituent at C-17 of finasteride did not perturb the mechanism of inhibition but significantly increased the rate of inhibition of type-1 5 alpha-reductase. The rate of inhibition was too fast to determine accurately when the normal substrate testosterone was used in the progress curve analysis as this inhibition rate is approaching the value of kcat/Km for the enzyme reaction.

PMID:
7577933
DOI:
10.1021/bi00041a024
[Indexed for MEDLINE]

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