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Endocrinology. 1981 Apr;108(4):1597-9.

Enzyme-generated intermediates derived from 4-androstene-3,6,17-trione and 1,4,6-androstatriene-3,17-dione cause a time-dependent decrease in human placental aromatase activity.

Abstract

Kinetic evidence is presented for a time-dependent decrease in human placental aromatase activity by enzyme-generated intermediates derived from two widely used steroids previously described as competitive inhibitors of estrogen biosynthesis. Thus, 4-androstene-3,6,17-trione binds to the enzyme with an apparent Ki of 0.43 microM and has a pseudo-first order overall rate constant for decrease in activity of 4.03x10(-3)sec-1, while 1,4,6-androstatriene-3,17-dione has an apparent Ki of 0.18 microM and a pseudo-first order overall rate constant for decrease in activity of 1.10x10(-3)sec-1. These findings imply that the potent inhibition of estrogen biosynthesis caused by these steroids results primarily from a decrease in enzyme activity caused by enzyme-generated intermediates from the parent steroids.

PMID:
7472286
DOI:
10.1210/endo-108-4-1597
[Indexed for MEDLINE]
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