19-oxygenations of 3-deoxy androgens, potent competitive inhibitors of estrogen biosynthesis, with human placental aromatase.
J Steroid Biochem Mol Biol
; 71(5-6): 173-9, 1999 Dec 31.
Article
in En
| MEDLINE
| ID: mdl-10704906
ABSTRACT
Aromatase is a cytochrome P450 enzyme complex that catalyzes the conversion of androst-4-ene-3,17-dione (AD) to estrone through three sequential oxygenations of the 19-methyl group. To gain insight into the ability of 3-deoxy derivative of AD, compound 1, and its 5-ene isomer 4, which are potent competitive inhibitors of aromatase, to serve as a substrate, we studied their 19-oxygenation by human placental aromatase and the metabolites isolated were analyzed by gas chromatography-mass spectrometry. Inhibitors 1 and 4 were found to be oxygenated with aromatase to produce the corresponding 19-hydroxy derivatives 2 and 5 and 19-oxo derivatives 3 and 6 as well as the 17beta-reduced 19-hydroxy compounds 7 and 8. Kinetic studies indicated that the 5-ene steroid 4 was surprisingly a good substrate for the aromatase-catalyzing 19-oxygenation with the V(max) value of 45 pmol/min per mg prot which was approx. four times higher than that of the other. The relative K(m) value for steroids 1 and 4 obtained in this study is opposite from the relative K(i) value obtained previously in the inhibition study. The results reveal that there is a difference between a binding suitable for serving as an inhibitor of aromatase and a binding suitable for serving as a substrate of the enzyme in the 3-deoxy steroid series and the C-3 carbonyl group of AD is essential for a proper binding as a substrate to the active site of aromatase.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Placenta
/
Aromatase
/
Estrogen Receptor Modulators
/
Estrogens
/
Androgens
/
Androstenedione
Limits:
Humans
Language:
En
Journal:
J Steroid Biochem Mol Biol
Journal subject:
BIOLOGIA MOLECULAR
/
BIOQUIMICA
Year:
1999
Document type:
Article
Affiliation country:
Japón