{"id":"8181fd71-8847-5e09-b778-34d3f5731b9d","stable_key":"0ad8610d-d575-5870-b7cd-763a9f750783:copper-heph-ferroxidation","predicate":"oxidizes","statement":"Recombinant copper-containing human hephaestin oxidized Fe(II), with an apparent substrate Km of 2.1 micromolar.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"ebec5459-2ae2-5249-bc73-e98959600242","mechanism_event_label":"A copper enzyme changes iron into the form needed for the next transport step.","subject":{"id":"a89b5f9c-0a58-5ef6-8e27-b2a8747b26a0","slug":"heph","display_name":"Human hephaestin / HEPH","entity_type_key":"protein"},"object":{"id":"59d6d1cd-df32-5b58-b950-3188bc7b95d6","slug":"iron-ii","display_name":"Ferrous iron","entity_type_key":"ion"},"evidence_count":1,"mechanism_event":{"id":"ebec5459-2ae2-5249-bc73-e98959600242","stable_key":"0ad8610d-d575-5870-b7cd-763a9f750783:copper-heph-ferroxidation-event","event_type":"biochemical_relationship","label":"A copper enzyme changes iron into the form needed for the next transport step.","description":"Recombinant copper-containing human hephaestin oxidized Fe(II), with an apparent substrate Km of 2.1 micromolar.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"964be7ac-43bd-5f3e-8326-94f0590de67a","slug":"iron-iii","display_name":"Ferric iron","entity_type_key":"ion"},"role":"oxidized iron product","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"9f0afdde-1ec1-5c8a-bb5e-f3b2b75f67f6","slug":"copper","display_name":"Copper","entity_type_key":"nutrient_element"},"role":"enzyme-bound metal","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"a89b5f9c-0a58-5ef6-8e27-b2a8747b26a0","slug":"heph","display_name":"Human hephaestin / HEPH","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"59d6d1cd-df32-5b58-b950-3188bc7b95d6","slug":"iron-ii","display_name":"Ferrous iron","entity_type_key":"ion"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_span","value_text":"{\"source_cache\": \"artifacts/copper-research/16274220.abstract.txt\", \"locator\": \"Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"7f88de566cf98e9aad1df97f91b7b37a4d8e685b842c164db25a196b09c0b976\", \"start_char\": 0, \"end_char\": 1880, \"text_sha256\": \"7f88de566cf98e9aad1df97f91b7b37a4d8e685b842c164db25a196b09c0b976\"}","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified recombinant human hephaestin","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Fe(II) substrate and apotransferrin assays","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Soluble recombinant construct; average measured copper loading of 3.13 atoms is not a universal mature-protein stoichiometry.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Copper research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"copper","display_name":"Copper","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Human protein produced in baby hamster kidney cells","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"A copper enzyme changes iron into the form needed for the next transport step.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[copper-p16274220] Recombinant expression and functional characterization of human hephaestin: a multicopper oxidase with ferroxidase activity. (2005). https://pubmed.ncbi.nlm.nih.gov/16274220/ DOI: 10.1021/bi051559k","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified soluble hephaestin construct","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"927f7b0e-f8e3-52d4-9c4f-a7da1005957e","evidence_kind":"source_excerpt","locator":"Lines 767-778","start_line":767,"end_line":778,"excerpt":"### copper-heph-ferroxidation\nRecombinant copper-containing human hephaestin oxidized Fe(II), with an apparent substrate Km of 2.1 micromolar.\nCondition category: normal\nnutrient_topic: Copper research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: A copper enzyme changes iron into the form needed for the next transport step.\norganism: Human protein produced in baby hamster kidney cells\ntissue_or_cell_type: Purified soluble hephaestin construct\nexperimental_model: Purified recombinant human hephaestin\nlimitations: Soluble recombinant construct; average measured copper loading of 3.13 atoms is not a universal mature-protein stoichiometry.\nexposure: Fe(II) substrate and apotransferrin assays\nevidence_span: {\"source_cache\": \"artifacts/copper-research/16274220.abstract.txt\", \"locator\": \"Exact primary indexed abstract; zero-based, end-exclusive Unicode character offsets\", \"file_sha256\": \"7f88de566cf98e9aad1df97f91b7b37a4d8e685b842c164db25a196b09c0b976\", \"start_char\": 0, \"end_char\": 1880, \"text_sha256\": \"7f88de566cf98e9aad1df97f91b7b37a4d8e685b842c164db25a196b09c0b976\"}\n[copper-p16274220] Recombinant expression and functional characterization of human hephaestin: a multicopper oxidase with ferroxidase activity. (2005). https://pubmed.ncbi.nlm.nih.gov/16274220/ DOI: 10.1021/bi051559k","model_system":"Purified recombinant human hephaestin","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [copper-p16274220] Recombinant expression and functional characterization of human hephaestin: a multicopper oxidase with ferroxidase activity. (2005). https://pubmed.ncbi.nlm.nih.gov/16274220/ DOI: 10.1021/bi051559k","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"9afba495-cbdc-51aa-998e-70a930dba3be","stable_key":"import-0ad8610d-d575-5870-b7cd-763a9f750783","title":"Copper: transport, cuproenzymes, deficiency, excess and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. 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