Characterization of an NADPH-dependent 17α-hydroxysteroid dehydrogenase encoded by the desF gene from the gut bacterium Clostridium scindens VPI 12708

Abstract

Epitestosterone (epiT) is the isomer of the androgen testosterone. Historically, the role of epiT has remained unclear. Recently, it has been reported that epiT promotes AR-dependent prostate cancer cell proliferation. The gut bacterium Clostridium scindens VPI 12708 converts androstenedione (AD) to epiT. The bacterial enzymatic pathways involved in epiT formation have been reported, where the desF gene that encodes 17-hydroxysteroid dehydrogenase converts AD to epiT using NADPH as a cofactor. In this study, we quantitatively characterized DesF kinetic parameters and substrate specificity. The results revealed that the optimal pH for the reductive reaction is 7.0, and for the oxidative reaction it is 7.5 and 8.0. The kinetic analysis showed that for the reductive reaction, the KM was 8.67 {+/-} 2.04 {micro}M and the Vmax was 1.95 {+/-} 0.11 {micro}M min-1; for the oxidative direction, the KM was 27.17 {+/-} 3.56 {micro}M and the Vmax was 2.18 {+/-} 0.08 {micro}M min-1. Moreover, the substrate specificity analysis revealed that 11-keto-AD is the most favourable substrate for DesF, and the 17-keto group of 11-keto-AD can be converted to the 17-hydroxy group. These results are a significant advance in understanding epiT formation by the gut microbiome.