{"id":"36b2c5c2-da2a-5eeb-b14d-3576be75c5bc","stable_key":"1310afbd-6010-586e-805d-551d846da421:b6-transport-alpl-ecto","predicate":"dephosphorylates","statement":"Human fibroblast ALPL hydrolyzed extracellular micromolar PLP at physiological pH; intact-cell and PI-PLC experiments supported lipid-anchored ecto-orientation.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"7d8685ad-93e4-5083-99a5-c786b3cd03b7","mechanism_event_label":"Cell-surface ALPL processes PLP outside the cell.","subject":{"id":"3148c377-9b4c-56ca-bc36-081bf1905d57","slug":"alpl","display_name":"Tissue-nonspecific alkaline phosphatase ALPL / TNAP","entity_type_key":"protein"},"object":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"7d8685ad-93e4-5083-99a5-c786b3cd03b7","stable_key":"1310afbd-6010-586e-805d-551d846da421:b6-transport-alpl-ecto-event","event_type":"biochemical_relationship","label":"Cell-surface ALPL processes PLP outside the cell.","description":"Human fibroblast ALPL hydrolyzed extracellular micromolar PLP at physiological pH; intact-cell and PI-PLC experiments supported lipid-anchored ecto-orientation.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"9bf6269d-9e01-553d-bd8b-11a0d613bfca","slug":"pyridoxal","display_name":"Pyridoxal","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"b28dfc54-a5ef-5f9e-ac1f-890b68e58dc3","slug":"inorganic-phosphate","display_name":"Inorganic phosphate","entity_type_key":"chemical_species"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"3148c377-9b4c-56ca-bc36-081bf1905d57","slug":"alpl","display_name":"Tissue-nonspecific alkaline phosphatase ALPL / TNAP","entity_type_key":"protein"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"6b656ff5-9532-5da4-8eea-8ca163a48649","slug":"pyridoxal-phosphate","display_name":"PLP","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""}]},"contexts":[{"dimension":"evidence_location","value_text":"Indexed abstract: intact/disrupted cells, PI-PLC and patient enzyme activity","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Normal and hypophosphatasia human skin fibroblasts.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Extracellular PLP; intact versus disrupted cells; PI-PLC release.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Directly demonstrated in fibroblasts; does not itself measure brain entry.","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":"Cell-surface ALPL processes PLP outside the cell.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[fedde1990] Alkaline phosphatase (tissue-nonspecific isoenzyme) is a phosphoethanolamine and pyridoxal-5'-phosphate ectophosphatase: normal and hypophosphatasia fibroblast study. (1990). https://pubmed.ncbi.nlm.nih.gov/2220817/","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Skin fibroblasts","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"e9344efe-1778-547f-a5e0-2313d23d27a8","evidence_kind":"source_excerpt","locator":"Lines 309-320","start_line":309,"end_line":320,"excerpt":"### b6-transport-alpl-ecto\nHuman fibroblast ALPL hydrolyzed extracellular micromolar PLP at physiological pH; intact-cell and PI-PLC experiments supported lipid-anchored ecto-orientation.\nCondition category: normal\nnutrient_topic: Vitamin B6 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Cell-surface ALPL processes PLP outside the cell.\norganism: Homo sapiens\ntissue_or_cell_type: Skin fibroblasts\nexperimental_model: Normal and hypophosphatasia human skin fibroblasts.\nlimitations: Directly demonstrated in fibroblasts; does not itself measure brain entry.\nexposure: Extracellular PLP; intact versus disrupted cells; PI-PLC release.\nevidence_location: Indexed abstract: intact/disrupted cells, PI-PLC and patient enzyme activity\n[fedde1990] Alkaline phosphatase (tissue-nonspecific isoenzyme) is a phosphoethanolamine and pyridoxal-5'-phosphate ectophosphatase: normal and hypophosphatasia fibroblast study. (1990). https://pubmed.ncbi.nlm.nih.gov/2220817/","model_system":"Normal and hypophosphatasia human skin fibroblasts.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [fedde1990] Alkaline phosphatase (tissue-nonspecific isoenzyme) is a phosphoethanolamine and pyridoxal-5'-phosphate ectophosphatase: normal and hypophosphatasia fibroblast study. (1990). https://pubmed.ncbi.nlm.nih.gov/2220817/","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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