Conversion of a 3-desoxysteroid to 3-desoxyestrogen by human placental aromatase.
Human placental aromatase is a cytochrome P-450 enzyme system which converts androgens to estrogens by three successive oxidative reactions. The first two steps have been shown to be hydroxylations at the androgen 19-carbon, but the third step remains unknown. A leading theory for the third step involves ferric peroxide attack on the 19-oxo group to produce a 19,19-hydroxyferric peroxide intermediate and subsequent collapse to estrogen. We had previously developed a nonenzymatic peroxide model reaction which was based on the above-mentioned theory, and we demonstrated the importance of 3-ketone enolization in facilitating aromatization. This study discusses the synthesis and nonenzymatic and enzymatic study of a 3-desoxy-2,4-diene-19-oxo androgen analogue. This compound was found to be a potent nonenzymatic model substrate and competitive inhibitor of aromatase (Ki = 73 nM). Furthermore, in an unprecedented event, this compound served as a substrate for aromatase, with conversion to the corresponding 3-desoxyestrogen.
Cole
P A
PA
Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Bean
J M
JM
Robinson
C H
CH
D001141:Aromatase / Q000378:metabolism*; D001667:Binding, Competitive; D004967:Estrogens / Q000096:biosynthesis; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013256:Steroids / Q000138:chemical synthesis*; D013379:Substrate Specificity
D004967:Estrogens; D007202:Indicators and Reagents; D013256:Steroids; D001141:Aromatase