Metabolism of 19-methyl-substituted steroids by human placental aromatase

Journal Article · Tue Dec 01 04:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00398a045· OSTI ID:5433753

Beusen, D D; Carrell, H L; Covey, D F

The 19-methyl analogues of androstenedione and its aromatization intermediates (19-hydroxyandrostenedione and 19-oxoandrostenedione) were evaluated as substrates of microsomal aromatase in order to determine the effect of a 19-alkyl substituent on the enzyme's regiospecificity. Neither the androstenedione analog (10-ethylestr-4-ene-3,17-dione (1c) nor the 19-oxoandrostenedione analog (10-acetylestr-4-ene-3,17-dione (3c)) was converted to estrogens or oxygenated metabolites by placental microsomes. In contrast, both analogues of 19-hydroxyandrostenedione (10-((1S)-1-hydroxyethyl) extr-4-ene-3,17-dione (2c) and 10-((1R)-1-hydroxyethyl)estr-4-ene-3,17-dione (2e)) were converted to the intermediate analog 3c in a process requiring O/sub 2/ and either NADH or NADPH. No change in enzyme regiospecificity was detected. The absolute configuration of 2e was determined by X-ray crystallography. Experiments with /sup 18/O/sub 2/ established that 3c generated from 2c retained little /sup 18/O (< 3%), while 3c arising from 2e retained a significant amount of /sup 18/O (approx. = 70%). All four 19-methyl steroids elicited type I difference spectra from placental microsomes in addition to acting as competitive inhibitors of aromatase. Pretreatment of microsomes with 4-hydroxyandrostenedione (a suicide inactivator of aromatase) abolished the metabolism of 2c and 2e to 3c, as well as the type I difference spectrum elicited by 2c and 2e. The failure of 2c, 2e, and 3c to undergo aromatization was rationalized in the context of a mechanistic proposal for the third oxygenation of aromatase requiring hydrogen abstraction at C/sub 1/ of 19,19-dihydroxyandrostenedione, homolytic cleavage of the C/sub 10/-C/sub 19/ bond, and oxygen rebound at C/sub 19/.

• Research Organization: Washington Univ. School of Medicine, St. Louis, MO
• OSTI ID: 5433753
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:24; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

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59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
ANDROGENS
ANDROSTANES
ANDROSTENEDIONE
AROMATIZATION
CELL CONSTITUENTS
CHEMICAL REACTIONS
COHERENT SCATTERING
DIFFRACTION
ENZYMES
EVEN-EVEN NUCLEI
FETAL MEMBRANES
HORMONES
ISOTOPES
KETONES
LABELLED COMPOUNDS
LIGHT NUCLEI
MEMBRANES
METABOLISM
MICROSOMES
NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
OXIDOREDUCTASES
OXYGEN 18
OXYGEN ISOTOPES
OXYGENASES
PLACENTA
REACTION INTERMEDIATES
SCATTERING
STABLE ISOTOPES
STEROID HORMONES
STEROIDS
SUBSTRATES
TRITIUM COMPOUNDS
X-RAY DIFFRACTION