Aromatization of testosterone and 19-nortestosterone by a single enzyme from equine testicular microsomes. Differences from human placental aromatase.

The study found that a single enzyme produced in the stallion testis can convert both testosterone and 19-nortestosterone into aromatic compounds. Despite the process being similar to aromatase found in human placenta, the study suggests that the enzyme from horse testis and that of human placenta are not the same due to the differences in the rate, preferential substrate, and response to monovalent cations.

Enzyme Aromatization

• The research focused on an enzyme found in the testes of stallions, which facilitated the aromatization, or conversion, of both testosterone and 19-nortestosterone into aromatic compounds.
• This enzyme displayed a lower affinity for nortestosterone in comparison to testosterone, signifying less binding strength and therefore a reduced ability to convert nortestosterone into its aromatic form.

Comparison with Human Aromatase

• Contrary to the human placental enzyme, known as aromatase or estrogen synthetase, the equine enzyme was able to aromatize testosterone and 19-nortestosterone with a similar degree of efficiency.
• Human aroma enzyme shows a preferential conversion of androgens to estrogen.

Noted Differences and Implications

• Differences were observed concerning the effects of monovalent cations, the way testosterone and 19-nortestosterone inhibit the aromatization of the compound androstenedione, and the rate of norandrogen aromatization.
• These observed differences led researchers to conclude that the testicular enzyme found in stallions is not identical to the aromatase found in the human placenta, suggesting potential differences in their biological functions.