{"id":"2d35b610-8a35-581c-938e-2339ee5b4cef","stable_key":"1310afbd-6010-586e-805d-551d846da421:b6-transport-caco2-pn-uptake","predicate":"undergoes","statement":"Caco-2 pyridoxine uptake was energy-dependent and sodium-independent; saturation occurred at pH 5.5 (apparent Km 11.99 micromolar), but not pH 7.4.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"4eb7118c-1c35-5388-ab83-5d8b3f01ed24","mechanism_event_label":"Acidic conditions exposed a saturable uptake component.","subject":{"id":"aa6648f2-8962-5567-9939-ef4145e40ed1","slug":"pyridoxine","display_name":"Pyridoxine","entity_type_key":"small_molecule"},"object":{"id":"e865ed43-8e30-5a99-ba28-3216d483c062","slug":"intestinal-pyridoxine-uptake","display_name":"Intestinal pyridoxine uptake","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"4eb7118c-1c35-5388-ab83-5d8b3f01ed24","stable_key":"1310afbd-6010-586e-805d-551d846da421:b6-transport-caco2-pn-uptake-event","event_type":"biochemical_relationship","label":"Acidic conditions exposed a saturable uptake component.","description":"Caco-2 pyridoxine uptake was energy-dependent and sodium-independent; saturation occurred at pH 5.5 (apparent Km 11.99 micromolar), but not pH 7.4.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"aa6648f2-8962-5567-9939-ef4145e40ed1","slug":"pyridoxine","display_name":"Pyridoxine","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"e865ed43-8e30-5a99-ba28-3216d483c062","slug":"intestinal-pyridoxine-uptake","display_name":"Intestinal pyridoxine uptake","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"evidence_location","value_text":"Indexed abstract: pH-dependent saturation and sodium independence","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human Caco-2 intestinal epithelial cells.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Radiotracer uptake at controlled extracellular pH.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Carrier identity was not established; uptake behavior alone does not identify a transporter gene.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-b6","display_name":"Vitamin B6","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Acidic conditions exposed a saturable uptake component.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[said2003] A carrier-mediated mechanism for pyridoxine uptake by human intestinal epithelial Caco-2 cells: regulation by a PKA-mediated pathway. (2003). https://pubmed.ncbi.nlm.nih.gov/12867360/ DOI: 10.1152/ajpcell.00204.2003","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Caco-2 cells","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"6ac069d4-16fc-5c49-b29f-657a2e4d3f99","evidence_kind":"source_excerpt","locator":"Lines 111-122","start_line":111,"end_line":122,"excerpt":"### b6-transport-caco2-pn-uptake\nCaco-2 pyridoxine uptake was energy-dependent and sodium-independent; saturation occurred at pH 5.5 (apparent Km 11.99 micromolar), but not pH 7.4.\nCondition category: normal\nnutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Acidic conditions exposed a saturable uptake component.\norganism: Homo sapiens\ntissue_or_cell_type: Caco-2 cells\nexperimental_model: Human Caco-2 intestinal epithelial cells.\nlimitations: Carrier identity was not established; uptake behavior alone does not identify a transporter gene.\nexposure: Radiotracer uptake at controlled extracellular pH.\nevidence_location: Indexed abstract: pH-dependent saturation and sodium independence\n[said2003] A carrier-mediated mechanism for pyridoxine uptake by human intestinal epithelial Caco-2 cells: regulation by a PKA-mediated pathway. (2003). https://pubmed.ncbi.nlm.nih.gov/12867360/ DOI: 10.1152/ajpcell.00204.2003","model_system":"Human Caco-2 intestinal epithelial cells.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [said2003] A carrier-mediated mechanism for pyridoxine uptake by human intestinal epithelial Caco-2 cells: regulation by a PKA-mediated pathway. (2003). https://pubmed.ncbi.nlm.nih.gov/12867360/ DOI: 10.1152/ajpcell.00204.2003","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"251773bb-16f5-5903-b135-db4a61d9dec4","stable_key":"import-1310afbd-6010-586e-805d-551d846da421","title":"Vitamin B6: mechanisms, 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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