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Publication Abstract from PubMed

Anaerobic bacteria inhabiting the human gastrointestinal tract have evolved various enzymes that modify host-derived steroids. The bacterial steroid-17,20-desmolase pathway cleaves the cortisol side-chain, forming pro-androgens predicted to impact host physiology. Bacterial 20beta-hydroxysteroid dehydrogenase (20beta-HSDH) regulates cortisol side-chain cleavage by reducing the C-20 carboxyl group on cortisol, yielding 20beta-dihydrocortisol. Recently, the gene encoding 20beta-HSDH in Butyricicoccus desmolans ATCC 43058 was reported, and a non-redundant protein search yielded a candidate 20beta-HSDH gene in Bifidobacterium adolescentis strain L2-32. B. adolescentis 20beta-HSDH could regulate cortisol side-chain cleavage by limiting pro-androgen formation in bacteria such as Clostridium scindens and 21-dehydroxylation by Eggerthella lenta Here, the putative B. adolescentis 20beta-HSDH was cloned, overexpressed and purified. 20beta-HSDH activity was confirmed through whole cell and pure enzymatic assays and it is specific for cortisol. Next, we solved the structures of recombinant 20beta-HSDH in both the apo and holo forms at 2.0-2.2A resolutions, revealing close overlap except for rearrangements near the active site. Interestingly, the structures contain a large, flexible N-terminal region which was investigated by gel filtration chromatography and CD spectroscopy. This extended N-terminus is important for protein stability because deletions of varying lengths caused structural changes and reduced enzymatic activity. A nonconserved extended N-terminus was also observed in several short-chain dehydro-genase/reductase family members. B. adolescentis strains capable of 20beta-HSDH activity could alter glucocorticoid metabolism in the gut and thereby serve as potential probiotics for the management of androgen-dependent diseases.

Structural and biochemical characterization of 20beta-hydroxysteroid dehydrogenase from Bifidobacterium adolescentis strain L2-32.,Doden HL, Pollet RM, Mythen SM, Wawrzak Z, Devendran S, Cann I, Koropatkin NM, Ridlon JM J Biol Chem. 2019 Jun 17. pii: RA119.009390. doi: 10.1074/jbc.RA119.009390. PMID:31209107^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.