{"id":"335fd007-0cda-5d04-a09d-1ff520864733","stable_key":"911fb3c7-8cc3-5667-b677-5682fab67648:histidine-urda-product","predicate":"forms_tested","statement":"Full-length and two-domain S. oneidensis UrdA converted urocanate to imidazole propionate and did not show the tested fumarate-reductase activity.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"9bfd4043-464e-572a-961f-f4125dcc3a94","mechanism_event_label":"A bacterial enzyme sends a histidine-derived intermediate down a different branch.","subject":{"id":"206711aa-90bc-5f09-a2d1-d9541f859f9f","slug":"shewanella-oneidensis-urda","display_name":"Shewanella oneidensis MR-1 urocanate reductase / UrdA","entity_type_key":"protein"},"object":{"id":"06c093ed-025c-54bc-8016-6a3da64ffbf9","slug":"imidazole-propionate","display_name":"Imidazole propionate","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"9bfd4043-464e-572a-961f-f4125dcc3a94","stable_key":"911fb3c7-8cc3-5667-b677-5682fab67648:histidine-urda-product-event","event_type":"observed_relationship","label":"A bacterial enzyme sends a histidine-derived intermediate down a different branch.","description":"Full-length and two-domain S. oneidensis UrdA converted urocanate to imidazole propionate and did not show the tested fumarate-reductase activity.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"206711aa-90bc-5f09-a2d1-d9541f859f9f","slug":"shewanella-oneidensis-urda","display_name":"Shewanella oneidensis MR-1 urocanate reductase / UrdA","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"06c093ed-025c-54bc-8016-6a3da64ffbf9","slug":"imidazole-propionate","display_name":"Imidazole propionate","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"44374451-3436-5136-a8ae-5dcc6d8c353b","slug":"histidine","display_name":"L-Histidine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"86f82ca3-8f80-5c1f-b724-27b78660c2a9","slug":"trans-urocanate","display_name":"trans-Urocanate","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"e2cd7179-f218-54e8-9ce9-7a836ae35fac","slug":"fad","display_name":"FAD","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary full text","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified bacterial full-length/truncated proteins, activity assays and ligand-bound crystal structures.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"This species is a structural model; abundance or flux in an individual human microbiome is not measured.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Histidine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"histidine","display_name":"L-Histidine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"A bacterial enzyme sends a histidine-derived intermediate down a different branch.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Structural characterization of the microbial enzyme urocanate reductase mediating imidazole propionate production. · 2021 · https://pubmed.ncbi.nlm.nih.gov/33649331/ · DOI 10.1038/s41467-021-21548-y","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"1e4264bd-46a9-5bd1-8ed2-0d90ce193a4a","evidence_kind":"source_excerpt","locator":"Lines 266-272","start_line":266,"end_line":272,"excerpt":"## histidine-urda-product\nA bacterial enzyme sends a histidine-derived intermediate down a different branch.\nFull-length and two-domain S. oneidensis UrdA converted urocanate to imidazole propionate and did not show the tested fumarate-reductase activity.\nModel: Purified bacterial full-length/truncated proteins, activity assays and ligand-bound crystal structures.\nLimitations: This species is a structural model; abundance or flux in an individual human microbiome is not measured.\nEvidence access: Primary full text\nStructural characterization of the microbial enzyme urocanate reductase mediating imidazole propionate production. · 2021 · https://pubmed.ncbi.nlm.nih.gov/33649331/ · DOI 10.1038/s41467-021-21548-y","model_system":"Purified bacterial full-length/truncated proteins, activity assays and ligand-bound crystal structures.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"ce59e6c9-1213-523b-9d0b-400b7a81cd1c","stable_key":"import-911fb3c7-8cc3-5667-b677-5682fab67648","title":"L-Histidine: supply, catabolism, histamine, receptors and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. 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