Identification and characterization of a 20β-HSDH from the anaerobic gut bacterium ATCC 43058.

Members of the gastrointestinal microbiota are known to convert glucocorticoids to androstanes, which are subsequently converted to potent androgens by other members of the gut microbiota or host tissues. and have previously been reported for steroid-17,20-desmolase and 20β-hydroxysteroid dehydrogenase (HSDH) activities that are responsible for androstane formation from cortisol; however, the genes encoding these enzymes have yet to be reported. In this work, we identified and located a gene encoding 20β-HSDH in both and The 20β-HSDH of was heterologously overexpressed and purified from The enzyme was determined to be a homotetramer with subunit molecular mass of 33.8 ± 3.7 kDa. The r20β-HSDH displayed pH optimum in the reductive direction at pH 9.0 and in the oxidative direction at pH 7.0-7.5 with (20β-dihydro)cortisol and NAD(H) as substrates. Cortisol is the preferred substrate with , 0.80 ± 0.06 μM; , 30.36 ± 1.97 μmol·min; , 607 ± 39 μmol·μM·min; / , 760 ± 7.67. Phylogenetic analysis of the 20β-HSDH from suggested that the 20β-HSDH is found in several , one of which was shown to express 20β-HSDH activity. Notably, we also identified a novel steroid-17,20-desmolase-elaborating bacterium, , a normal inhabitant of the urinary tract.