Antisera against estrogen synthetase from human placental microsomes. Antibody characterization and cross-reactivity studies in other organs.

Antibodies were obtained against both protein components of the cytochrome P-450 enzyme system responsible for estrogen biosynthesis, estrogen synthetase (aromatase), from human placental microsomes. The antiserum against the NADPH-cytochrome P-450 reductase component (antiserum denoted RE-DFBIV) gave a single major band at the Mr of the authentic enzyme by immunoblotting after electrophoretic separation of SDS-solubilized microsomes and inhibited both the reductase and aromatase activities in human placental and endometrial microsomes (Tseng, L. and Bellino, F.L. (1985) J. Steroid Biochem. 22, 555-557) and in homogenates of cultured aromatase-stimulated human endometrial stromal cells and human ovarian microsomes. The antiserum against the cytochrome P-450 component of aromatase (antiserum denoted P45FBIII) also gave a single band at the Mr of the authentic protein by immunoblotting after electrophoresis, and inhibited aromatase activity in homogenates of human placental microsomes, ovarian and decidual particulate fractions and cultured aromatase-stimulated endometrial stromal cells. This antiserum had no effect on NADPH-cytochrome c reductase activity in any of the systems studied. We conclude that these antiserum preparations separately recognize the NADPH-cytochrome P-450 reductase and cytochrome P-450 components of aromatase in human placenta, ovary, decidua and endometrium. Epitopes on these aromatase component proteins involved in enzyme activity are shared among these various human tissue sources.