A patchwork pathway for oxygenase‐independent degradation of side chain containing steroids |
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Authors: | Markus Warnke Christian Jacoby Tobias Jung Michael Agne Mario Mergelsberg Robert Starke Nico Jehmlich Martin von Bergen Hans‐Hermann Richnow Thomas Brüls Matthias Boll |
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Institution: | 1. Institute of Biology II, Microbiology, Albert‐Ludwigs‐University Freiburg, Freiburg, Germany;2. Spemann Graduate School of Biology and Medicine (SGBM), Albert‐Ludwigs‐University Freiburg, Freiburg, Germany;3. Department of Molecular Systems Biology, Helmholtz Centre of Environmental Sciences, Leipzig, Germany;4. Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, University of Leipzig, Leipzig, Germany;5. Department of Isotope Biogeochemistry, Helmholtz Centre of Environmental Sciences, Leipzig, Germany;6. CEA, DRF, IG, Genoscope, Evry, France;7. CNRS‐UMR8030, Université d'Evry Val d'Essonne and Université Paris‐Saclay, Evry, France |
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Abstract: | The denitrifying betaproteobacterium Sterolibacterium denitrificans serves as model organism for studying the oxygen‐independent degradation of cholesterol. Here, we demonstrate its capability of degrading various globally abundant side chain containing zoo‐, phyto‐ and mycosterols. We provide the complete genome that empowered an integrated genomics/proteomics/metabolomics approach, accompanied by the characterization of a characteristic enzyme of steroid side chain degradation. The results indicate that individual molybdopterin‐containing steroid dehydrogenases are involved in C25‐hydroxylations of steroids with different isoprenoid side chains, followed by the unusual conversion to C26‐oic acids. Side chain degradation to androsta‐1,4‐diene‐3,17‐dione (ADD) via aldolytic C–C bond cleavages involves acyl‐CoA synthetases/dehydrogenases specific for the respective 26‐, 24‐ and 22‐oic acids/‐oyl‐CoAs and promiscuous MaoC‐like enoyl‐CoA hydratases, aldolases and aldehyde dehydrogenases. Degradation of rings A and B depends on gene products uniquely found in anaerobic steroid degraders, which after hydrolytic cleavage of ring A, again involves CoA‐ester intermediates. The degradation of the remaining CD rings via hydrolytic cleavage appears to be highly similar in aerobic and anaerobic bacteria. Anaerobic cholesterol degradation employs a composite repertoire of more than 40 genes partially known from aerobic degradation in gammaproteobacteria/actinobacteria, supplemented by unique genes that are required to circumvent oxygenase‐dependent reactions. |
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