Aromatization of testosterone and 19-nortestosterone by a single enzyme from equine testicular microsomes. Differences from human placental aromatase.
A single enzyme in the stallion testis was able to aromatize both testosterone and nortestosterone. This enzyme had a much lower affinity for nortestosterone than for testosterone. In contrast to human placental estrogen synthetase, this enzyme aromatized testosterone and 19-nortestosterone with similar efficiency. The differences observed (effects of monovalent cations, inhibition of androstenedione aromatization by testosterone and 19-nortestosterone and, above all, rate of norandrogen aromatization) suggest that the aromatase in the horse testis is not the same as that in the human placenta.
Silberzahn
P
P
Laboratoire de Biochimie, UA CNRS 609, Caen, France.
Gaillard
J L
JL
Quincey
D
D
Dintinger
T
T
Al-Timimi
I
I
D000818:Animals; D001141:Aromatase / Q000378:metabolism*; D005260:Female; D006736:Horses; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology* / Q000378:metabolism; D009277:Nandrolone / Q000378:metabolism*; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013737:Testis / Q000201:enzymology* / Q000378:metabolism; D013739:Testosterone / Q000378:metabolism*
D013739:Testosterone; D009277:Nandrolone; D001141:Aromatase