Figure 5. OsrA is a 3-oxo-Δ¹-reductase essential for complete reduction of synthetic corticosteroids.

(A) Structure of synthetic corticosteroids used in assays. (B) Products formed from synthetic corticosteroids following incubation with C. steroidoreducens HCS.1 cells. (C) Percent prednisolone conversion to cortisol following incubation of E. coli cells with osrA- and osrB-expressing plasmids or an empty vector control. (D) C. steroidoreducens HCS.1 steroid reduction pathway identified in this study.