Cytochrome b5-mediated redox cycling of estrogen Article

Roy, D, Strobel, HW, Liehr, JG. (1991). Cytochrome b5-mediated redox cycling of estrogen . 285(2), 331-338. 10.1016/0003-9861(91)90368-S

cited authors

  • Roy, D; Strobel, HW; Liehr, JG

fiu authors


  • Previously, we have demonstrated microsomal cytochrome P450-catalyzed redox cycling of estrogens. In this study, we investigated the role of cytochrome b5 in redox cycling in order to obtain a full understanding of enzymatic contributions to redox reactions of estrogens. Pure cytochrome P450c and hydrogen peroxide or cumene hydroperoxide oxidized diethylstilbestrol (DES) to diethylstilbestrol-4′,4″-quinone (DES Q). This oxidation by H2O2 was doubled by addition of cytochrome b5 to cytochrome P450c (molar ratio of 1:4), but did not proceed with cytochrome b5 alone. The stimulation by cytochrome b5 of the cytochrome P450c-catalyzed oxidation of DES to DES Q occurred via modulation of the Vmax of cytochrome P450c rather than of the Km. DES Q was reduced to DES by purified cytochrome b5 and NADH-dependent cytochrome b5 reductase. Pretreatment of microsomes with an antibody to cytochrome b5 reductase inhibited microsomal NADH-dependent reduction of DES Q to DES by 55%. Cytochrome b5 likely participates in the oxidation of DES to DES Q by interacting with cytochrome P450c and in the reduction of DES Q to DES by interacting with cytochrome b5 reductase. Thus, the study demonstrates that cytochrome b5 plays an active role in biological oxidation and reduction reactions. © 1991.

publication date

  • January 1, 1991

Digital Object Identifier (DOI)

start page

  • 331

end page

  • 338


  • 285


  • 2