Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
Biochemical Studies of Estr-4-ene-3, 6, 17-trione and 5α-Androstan-17-ones with or without a Carbonyl Function at C-3 and/or C-6 as Aromatase Inhibitors
Mitsuteru NUMAZAWAAyako MUTSUMIMii TACHIBANAMasao NAGAOKA
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1995 Volume 18 Issue 4 Pages 555-558

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Abstract

19-Nor (2) and 5α-reduced (3) derivatives of androst-4-ene-3, 6, 17-trione (1) as well as 5α-androstan-17-ones 4-6 were tested for their abilities to inhibit aromatase in human placental microsomes. All the steroids except 5α-6-one 4 were fair to good competitive inhibitors of the enzyme, with apparent Ki's ranging from 50 to 820 nM in which 5α-3-one 5 was the most potent among them. The inhibitory activities of the 19-nor and 5α-reduced derivatives (2 and 3) were less potent than that of the parent compound 1. Inhibitor 2 caused a time-dependent, pseudo-first-order inactivation of aromatase activity with a rate constant for inactivation of 0.148 min-1 in the presence of NADPH in air. The substrate androstenedione prevented the inactivation and L-cysteine did not protect aromatase from the inactivation.

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© The Pharmaceutical Society of Japan
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