{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/101047"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/101047","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Characterization of enzymatic pathways involved in cortisol and bile acid metabolism by the gut microbiota","abstract":"The gut microbiota consists of a complex network of distinct bacterial taxa that together affect the physiology of the human host. Of the many facets affected by gut microbiota, their impact on the endocrine system is both significant and understudied. The diversity observed in microbial isolates and operational taxonomic units from one human gut to another is due largely in part by the strain specific proteins expressed by the microbes that inhabit them. Some of these unique proteins have evolved to biotransform host sterols which can be reabsorbed by the body and potentially affect endocrine functions. Bacterial hydroxysteroid dehydrogenases (HSDHs) have the potential to significantly alter the physicochemical properties of bile acids with implications for increased/decreased toxicity for gut bacteria and the host. We located a gene-cluster in Eggerthella CAG:298 predicted to encode three HSDHs (CDD59473, CDD59474, CDD59475), synthesized the genes for heterologous expression in E. coli and then screened bile acid substrates against the purified recombinant enzymes, revealing novel 3-, 3-, and 12-HSDHs. We also developed an enzyme-linked continuous spectrophotometric assay to quantify steroid-17,20-desmolase activity from recombinant enzymes encoded by the desA and desB genes from Clostridium scindens ATCC 35704. Steroid-17,20-desmolase is responsible for the side chain cleavage that biotransforms cortisol into 11β-hydroxyandrostenedione (11β-OHAD). The reaction performed by the steroid-17,20-desmolase appears to be regulated via pyridine nucleotide-dependent HSDHs, which are capable of converting cortisol into a form unable to be utilized by steroid-17,20-desmolase. A recently identified 20β-HSDH from Bifidobacterium adolescentis strain L2-32 has been biochemically characterized and crystallized. This 20β-HSDH has the potential to directly affect androgen formation by functioning as a metabolic rheostat controlling the steroid-17,20-desmolase activity of Clostridium scindens ATCC 35704.","abstract_html":"The gut microbiota consists of a complex network of distinct bacterial taxa that together affect the physiology of the human host. Of the many facets affected by gut microbiota, their impact on the endocrine system is both significant and understudied. The diversity observed in microbial isolates and operational taxonomic units from one human gut to another is due largely in part by the strain specific proteins expressed by the microbes that inhabit them. Some of these unique proteins have evolved to biotransform host sterols which can be reabsorbed by the body and potentially affect endocrine functions. Bacterial hydroxysteroid dehydrogenases (HSDHs) have the potential to significantly alter the physicochemical properties of bile acids with implications for increased/decreased toxicity for gut bacteria and the host. We located a gene-cluster in Eggerthella CAG:298 predicted to encode three HSDHs (CDD59473, CDD59474, CDD59475), synthesized the genes for heterologous expression in E. coli and then screened bile acid substrates against the purified recombinant enzymes, revealing novel 3-, 3-, and 12-HSDHs. We also developed an enzyme-linked continuous spectrophotometric assay to quantify steroid-17,20-desmolase activity from recombinant enzymes encoded by the desA and desB genes from Clostridium scindens ATCC 35704. Steroid-17,20-desmolase is responsible for the side chain cleavage that biotransforms cortisol into 11β-hydroxyandrostenedione (11β-OHAD). The reaction performed by the steroid-17,20-desmolase appears to be regulated via pyridine nucleotide-dependent HSDHs, which are capable of converting cortisol into a form unable to be utilized by steroid-17,20-desmolase. A recently identified 20β-HSDH from Bifidobacterium adolescentis strain L2-32 has been biochemically characterized and crystallized. This 20β-HSDH has the potential to directly affect androgen formation by functioning as a metabolic rheostat controlling the steroid-17,20-desmolase activity of Clostridium scindens ATCC 35704.","abstract_has_math":false,"creators":["Mythen, Seán Martin"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Animal Sciences","degree_department":null,"school":null,"contributors":["Ridlon, Jason M"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-09-04T20:27:24Z","date_published":"2018-09-04T20:27:24Z","updated_at":"2026-07-22T22:24:38Z","subjects":["Cortisol","Steroid","Gut","Microbiota","Bile acid"],"languages":["en"],"rights":["Copyright 2018 Seán Martin Mythen"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/101047","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Ridlon, Jason M"]},{"key":"dc:creator","label":"Author","values":["Mythen, Seán Martin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-09-04T20:27:24Z","2018-04-24","2018-05"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Animal Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Cortisol","Steroid","Gut","Microbiota","Bile acid"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2018 Seán Martin Mythen"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/101047"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The gut microbiota consists of a complex network of distinct bacterial taxa that together affect the physiology of the human host. Of the many facets affected by gut microbiota, their impact on the endocrine system is both significant and understudied. The diversity observed in microbial isolates and operational taxonomic units from one human gut to another is due largely in part by the strain specific proteins expressed by the microbes that inhabit them. Some of these unique proteins have evolved to biotransform host sterols which can be reabsorbed by the body and potentially affect endocrine functions. Bacterial hydroxysteroid dehydrogenases (HSDHs) have the potential to significantly alter the physicochemical properties of bile acids with implications for increased/decreased toxicity for gut bacteria and the host. We located a gene-cluster in Eggerthella CAG:298 predicted to encode three HSDHs (CDD59473, CDD59474, CDD59475), synthesized the genes for heterologous expression in E. coli and then screened bile acid substrates against the purified recombinant enzymes, revealing novel 3-, 3-, and 12-HSDHs. We also developed an enzyme-linked continuous spectrophotometric assay to quantify steroid-17,20-desmolase activity from recombinant enzymes encoded by the desA and desB genes from Clostridium scindens ATCC 35704. Steroid-17,20-desmolase is responsible for the side chain cleavage that biotransforms cortisol into 11β-hydroxyandrostenedione (11β-OHAD). The reaction performed by the steroid-17,20-desmolase appears to be regulated via pyridine nucleotide-dependent HSDHs, which are capable of converting cortisol into a form unable to be utilized by steroid-17,20-desmolase. A recently identified 20β-HSDH from Bifidobacterium adolescentis strain L2-32 has been biochemically characterized and crystallized. This 20β-HSDH has the potential to directly affect androgen formation by functioning as a metabolic rheostat controlling the steroid-17,20-desmolase activity of Clostridium scindens ATCC 35704.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-08-31 without embargo terms","The student, Seán Mythen, accepted the attached license on 2018-04-23 at 13:28.","The student, Seán Mythen, submitted this Thesis for approval on 2018-04-23 at 13:34.","This Thesis was approved for publication on 2018-04-24 at 08:46.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12427 on 2018-08-31 at 17:14:18","Made available in DSpace on 2018-09-04T20:27:24Z (GMT). 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The diversity observed in microbial isolates and operational taxonomic units from one human gut to another is due largely in part by the strain specific proteins expressed by the microbes that inhabit them. Some of these unique proteins have evolved to biotransform host sterols which can be reabsorbed by the body and potentially affect endocrine functions. Bacterial hydroxysteroid dehydrogenases (HSDHs) have the potential to significantly alter the physicochemical properties of bile acids with implications for increased/decreased toxicity for gut bacteria and the host. We located a gene-cluster in Eggerthella CAG:298 predicted to encode three HSDHs (CDD59473, CDD59474, CDD59475), synthesized the genes for heterologous expression in E. coli and then screened bile acid substrates against the purified recombinant enzymes, revealing novel 3-, 3-, and 12-HSDHs. We also developed an enzyme-linked continuous spectrophotometric assay to quantify steroid-17,20-desmolase activity from recombinant enzymes encoded by the desA and desB genes from Clostridium scindens ATCC 35704. Steroid-17,20-desmolase is responsible for the side chain cleavage that biotransforms cortisol into 11β-hydroxyandrostenedione (11β-OHAD). The reaction performed by the steroid-17,20-desmolase appears to be regulated via pyridine nucleotide-dependent HSDHs, which are capable of converting cortisol into a form unable to be utilized by steroid-17,20-desmolase. A recently identified 20β-HSDH from Bifidobacterium adolescentis strain L2-32 has been biochemically characterized and crystallized. This 20β-HSDH has the potential to directly affect androgen formation by functioning as a metabolic rheostat controlling the steroid-17,20-desmolase activity of Clostridium scindens ATCC 35704.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-08-31 without embargo terms","The student, Seán Mythen, accepted the attached license on 2018-04-23 at 13:28.","The student, Seán Mythen, submitted this Thesis for approval on 2018-04-23 at 13:34.","This Thesis was approved for publication on 2018-04-24 at 08:46.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12427 on 2018-08-31 at 17:14:18","Made available in DSpace on 2018-09-04T20:27:24Z (GMT). No. of bitstreams: 2 MYTHEN-THESIS-2018.pdf: 4264690 bytes, checksum: 02dafb507fa9dceefdcb64df888ca5d5 (MD5) LICENSE.txt: 4208 bytes, checksum: a03ece0185edaaa3595114f62b55553e (MD5) Previous issue date: 2018-04-24"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/101047"],"dc:language":["en"],"dc:rights":["Copyright 2018 Seán Martin Mythen"],"dc:subject":["Cortisol","Steroid","Gut","Microbiota","Bile acid"],"dc:title":["Characterization of enzymatic pathways involved in cortisol and bile acid metabolism by the gut microbiota"],"dc:type":["text"],"thesis:degree_discipline":["Animal Sciences"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:38Z"}