Aromatase is localized in the endoplasmic reticulum where it is regulated by tissue-specific promoters that are in turn controlled by hormones, cytokines, and other factors.
It catalyzes the last steps of estrogen biosynthesis from androgens (specifically, it transforms androstenedione to estrone and testosterone to estradiol).
These steps include three successive hydroxylations of the 19-methyl group of androgens, followed by simultaneous elimination of the methyl group as formate and aromatization of the A-ring.

Androstenedione + 3O₂ + 3NADPH + 3H⁺  Estrone + Formate + 4H₂O + 3NADP⁺
Testosterone + 3O₂ + 3NADPH + 3H⁺  17β-estradiol + Formate + 4H₂O + 3NADP⁺
Aromatase is localized in the endoplasmic reticulum where it is regulated by tissue-specific promoters that are in turn controlled by hormones, cytokines, and other factors. It catalyzes the last steps of estrogen biosynthesis from androgens (specifically, it transforms androstenedione to estrone and testosterone to estradiol). These steps include three successive hydroxylations of the 19-methyl group of androgens, followed by simultaneous elimination of the methyl group as formate and aromatization of the A-ring.
Androstenedione + 3O₂ + 3NADPH + 3H⁺  Estrone + Formate + 4H₂O + 3NADP⁺
Testosterone + 3O₂ + 3NADPH + 3H⁺  17β-estradiol + Formate + 4H₂O + 3NADP⁺
Aromatase