{"id":"d114bb1a-acb0-5bba-9e25-105693727e10","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-tkt-calcium-thdp-anchor","predicate":"coordinates-with","statement":"In recombinant human TKT, Ca2+ coordinates the ThDP diphosphate and protein ligands at the active site.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"1f028a51-da8c-538a-9f52-da67720ba103","mechanism_event_label":"Calcium can anchor the B1-derived cofactor in active human transketolase.","subject":{"id":"e359bc15-e675-5d83-b0fe-1d70814e130b","slug":"calcium-ion","display_name":"Calcium ion","entity_type_key":"ion"},"object":{"id":"187db168-8028-5ce6-9f8b-4bc61ebad1a0","slug":"thiamine-diphosphate","display_name":"Thiamine diphosphate","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"1f028a51-da8c-538a-9f52-da67720ba103","stable_key":"0f17db03-207f-5910-ac8e-13dfc2f378ce:mg-tkt-calcium-thdp-anchor-event","event_type":"biochemical_relationship","label":"Calcium can anchor the B1-derived cofactor in active human transketolase.","description":"In recombinant human TKT, Ca2+ coordinates the ThDP diphosphate and protein ligands at the active site.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"c95c645c-ae67-5911-871e-4f796a17faec","slug":"tkt","display_name":"Human transketolase","entity_type_key":"protein"},"role":"cofactor-binding enzyme","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"bff427ab-35f9-59c2-bb24-fd5953bbaec2","slug":"magnesium-ion","display_name":"Mg2+","entity_type_key":"ion"},"role":"alternative metal in other TKT preparations","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"e359bc15-e675-5d83-b0fe-1d70814e130b","slug":"calcium-ion","display_name":"Calcium ion","entity_type_key":"ion"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"187db168-8028-5ce6-9f8b-4bc61ebad1a0","slug":"thiamine-diphosphate","display_name":"Thiamine diphosphate","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Magnesium availability supports vitamin B1 activation or cofactor use in the specified preparation; this does not establish a dietary threshold or universal treatment failure.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Recombinant human TKT crystallography, kinetics and NMR.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Ca-supported structural preparation does not quantify native human tissue metal occupancy.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Magnesium research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"magnesium","display_name":"Magnesium","entity_type_key":"nutrient_element"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Calcium can anchor the B1-derived cofactor in active human transketolase.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[mitschke-2010-tkt] The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action (2010). https://pmc.ncbi.nlm.nih.gov/articles/PMC2951230/ DOI: 10.1074/jbc.M110.149955","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Recombinant TKT crystals","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"e7ecf083-7269-5a82-a0e8-bca7bd0af8ad","evidence_kind":"source_excerpt","locator":"Lines 589-599","start_line":589,"end_line":599,"excerpt":"### mg-tkt-calcium-thdp-anchor\nIn recombinant human TKT, Ca2+ coordinates the ThDP diphosphate and protein ligands at the active site.\nCondition category: normal\nnutrient_topic: Magnesium research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Calcium can anchor the B1-derived cofactor in active human transketolase.\norganism: Homo sapiens\ntissue_or_cell_type: Recombinant TKT crystals\nexperimental_model: Recombinant human TKT crystallography, kinetics and NMR.\nlimitations: Ca-supported structural preparation does not quantify native human tissue metal occupancy.\ncross_nutrient: Magnesium availability supports vitamin B1 activation or cofactor use in the specified preparation; this does not establish a dietary threshold or universal treatment failure.\n[mitschke-2010-tkt] The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action (2010). https://pmc.ncbi.nlm.nih.gov/articles/PMC2951230/ DOI: 10.1074/jbc.M110.149955","model_system":"Recombinant human TKT crystallography, kinetics and NMR.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [mitschke-2010-tkt] The Crystal Structure of Human Transketolase and New Insights into Its Mode of Action (2010). https://pmc.ncbi.nlm.nih.gov/articles/PMC2951230/ DOI: 10.1074/jbc.M110.149955","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"dd101e28-1a2e-5a48-9d1e-809c77514866","stable_key":"import-0f17db03-207f-5910-ac8e-13dfc2f378ce","title":"Magnesium: cross-nutrient mechanisms and deficiency (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"e111c412f57143a17e8e65e74e8f7888b5bb9a61099873f4767f527fac19bb07","revision_id":"6b7f04f2-66ed-5859-955f-c2b50d4bf041","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}