[Aromatase: universal and complex enzymology].

Cytochrome P-450 aromatase (cytochrome P-450 XIXA1, EC 1.14.14.1) is a key enzyme of estrogen biosynthesis. This is the only enzyme that catalyzes the processes leading to aromatization of the first ring of the steroid nucleus, and, therefore, gives rise to estrogens - estrone, estradiol and estriol. Other estrogens - estriol, equiline and equilenine - are formed mainly by hydroxylation or dehydrogenation of estradiol, so aromatase can be considered the only enzyme that limits the formation of estrogen.