Catalytic differences between porcine blastocyst and placental aromatase isozymes

摘要: Two isozymes of porcine aromatase, the placental and blastocyst forms, were expressed in CHO cells using mammalian cell transfection method. Using an 'in-cell' assay (a 3H-water release method), catalytic parameters aromatase found to be very similar those human enzyme; however, activity isozyme was one-thirtieth that isozyme. Product isolation (using testosterone as substrate) revealed major steroid products 17beta-estradiol 19-nortestosterone. The product ratio estradiol/19-nortestosterone 94 : 6 for form, 92 8 wild-type aromatase. Therefore, catalyzes mainly androgen 19-desmethylation rather than aromatization. In addition, inhibition profile analyses on performed three steroidal inhibitors [4-hydroxyandro-stenedione (4-OHA), 7alpha-(4'-amino)phenylthio-1, 4-androstandiene-3,17-dione (7alpha-APTADD), bridge (2, 19-methyleneoxy) androstene-3,17-dione (MDL 101,003)], four nonsteroidal [aminoglutethimide (AG), CGS 20267, ICI D1033, vorozole (R83842)]. While two share 93% amino-acid sequence identity, our results indicate have distinct responses various inhibitors.