{"id":"c698090f-6b98-5b55-a521-09e8871c33ee","stable_key":"6d38d43e-01e4-5641-93be-65654271e242:zinc-enz-ca2-coordination","predicate":"coordinates_active_site_of","statement":"X-ray absorption analysis of human CA2 supported a zinc site with three histidine nitrogen ligands and most likely one water/hydroxide oxygen ligand in both isolated and reconstituted enzyme.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"99ff3477-af93-522e-bbc0-f8d46129f5fe","mechanism_event_label":"CA2 holds zinc with three histidines and a water-derived ligand at its active site.","subject":{"id":"49c806c2-7041-5020-8b3b-fa04ffa122ac","slug":"zinc-ion","display_name":"Zinc(II) ion","entity_type_key":"ion"},"object":{"id":"812cb56b-2561-5f29-98ec-4b8cc7f79a63","slug":"ca2","display_name":"Human carbonic anhydrase II / CA2","entity_type_key":"protein"},"evidence_count":1,"mechanism_event":{"id":"99ff3477-af93-522e-bbc0-f8d46129f5fe","stable_key":"6d38d43e-01e4-5641-93be-65654271e242:zinc-enz-ca2-coordination-event","event_type":"biochemical_relationship","label":"CA2 holds zinc with three histidines and a water-derived ligand at its active site.","description":"X-ray absorption analysis of human CA2 supported a zinc site with three histidine nitrogen ligands and most likely one water/hydroxide oxygen ligand in both isolated and reconstituted enzyme.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"d31225b7-8e94-5857-9ea1-67ac794b1f15","slug":"water","display_name":"H2O","entity_type_key":"small_molecule"},"role":"coordinating_solvent","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"49c806c2-7041-5020-8b3b-fa04ffa122ac","slug":"zinc-ion","display_name":"Zinc(II) ion","entity_type_key":"ion"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"812cb56b-2561-5f29-98ec-4b8cc7f79a63","slug":"ca2","display_name":"Human carbonic anhydrase II / CA2","entity_type_key":"protein"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified recombinant human CA2; metal reconstitution, ITC and X-ray absorption spectroscopy","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Zn K-edge XANES and EXAFS on isolated and zinc-reconstituted recombinant CA2.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Coordination assignment is spectroscopic; the oxygen ligand is most likely solvent-derived, not an independently measured dietary effect.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Zinc research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"zinc","display_name":"Zinc","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"CA2 holds zinc with three histidines and a water-derived ligand at its active site.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[zinc-enz-ca2-coordination2012] Revisiting zinc coordination in human carbonic anhydrase II. (2012). https://pubmed.ncbi.nlm.nih.gov/23030313/ DOI: 10.1021/ic301645j","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Purified protein; cell-free assay","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"30b8ffde-bcb2-53c2-9e13-b0369a806ef4","evidence_kind":"source_excerpt","locator":"Lines 651-662","start_line":651,"end_line":662,"excerpt":"### zinc-enz-ca2-coordination\nX-ray absorption analysis of human CA2 supported a zinc site with three histidine nitrogen ligands and most likely one water/hydroxide oxygen ligand in both isolated and reconstituted enzyme.\nCondition category: normal\nnutrient_topic: Zinc research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: CA2 holds zinc with three histidines and a water-derived ligand at its active site.\norganism: Homo sapiens\ntissue_or_cell_type: Purified protein; cell-free assay\nexperimental_model: Purified recombinant human CA2; metal reconstitution, ITC and X-ray absorption spectroscopy\nlimitations: Coordination assignment is spectroscopic; the oxygen ligand is most likely solvent-derived, not an independently measured dietary effect.\nexposure: Zn K-edge XANES and EXAFS on isolated and zinc-reconstituted recombinant CA2.\ncross_nutrient: false\n[zinc-enz-ca2-coordination2012] Revisiting zinc coordination in human carbonic anhydrase II. (2012). https://pubmed.ncbi.nlm.nih.gov/23030313/ DOI: 10.1021/ic301645j","model_system":"Purified recombinant human CA2; metal reconstitution, ITC and X-ray absorption spectroscopy","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [zinc-enz-ca2-coordination2012] Revisiting zinc coordination in human carbonic anhydrase II. (2012). https://pubmed.ncbi.nlm.nih.gov/23030313/ DOI: 10.1021/ic301645j","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"c5ee0fee-ce5c-58de-905a-10fb0ea0723c","stable_key":"import-6d38d43e-01e4-5641-93be-65654271e242","title":"Zinc: transport, enzyme loading, deficiency 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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