Open AccessDifferent in vitro metabolism of 7 α‐methyl‐19‐nortestosterone by human and equine aromatases
Author(s) -
MOSLEMI Safa,
DINTINGER Thierry,
DEHENNIN Louis,
SILBERZAHN Pierre,
GAILLARD JeanLuc
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb17955.x
Subject(s) - microsome , androstenedione , enzyme , metabolism , chemistry , biochemistry , microsoma , in vitro , human placenta , androgen , placenta , medicine , endocrinology , biology , fetus , hormone , pregnancy , genetics
The ability of human and equine placental microsomes to aromatize 7α‐methyl‐19‐nortestoster‐one (MNT) was studied. Kinetic analysis indicates that MNT shares the androgen‐binding site of human and equine placental microsomal aromastases. Human placental microsomal estrogen synthetase had about a 2.5‐fold higher relative affinity for MNT than the equine placental enzyme ( K iMNT / K m androstenedione of 32 versus 87). However, MNT was not metabolized by human placental microsomes, whereas it was very actively metabolized by equine placental microsomes. Further studies using purified equine cytochrome P ‐450 arom indicated that the presence of a 7α‐methyl group and the absence of a C19 methyl group did not impair its conversion by the purified enzyme. The product of this reaction was separated and identified as 7α‐methylestradiol by gas chromatography coupled to mass spectrometry.