{"id":"64a42d10-7fd9-5ade-ab20-f8dc5926db82","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:vc-enzyme-initial-p4h-turnover","predicate":"hydroxylates","statement":"Purified chick collagen prolyl hydroxylase completed approximately 15–30 rapid catalytic cycles in 5–10 seconds without added ascorbate before activity declined.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"a31f4167-8756-5011-bd65-cd8c818db53d","mechanism_event_label":"The collagen enzyme can start working without vitamin C, but sustained work needs vitamin C support.","subject":{"id":"00d6f82e-4f52-54ea-9121-c4d332c8cd53","slug":"chick-collagen-prolyl-4-hydroxylase","display_name":"Chick collagen prolyl 4-hydroxylase preparation","entity_type_key":"protein_complex"},"object":{"id":"0cf232e8-346d-54d2-97ee-659df9edaddb","slug":"collagen-proline-residues","display_name":"Collagen-bound proline residues","entity_type_key":"protein_state"},"evidence_count":1,"mechanism_event":{"id":"a31f4167-8756-5011-bd65-cd8c818db53d","stable_key":"cb568d28-484a-5c2e-9fcc-2d780358e514:vc-enzyme-initial-p4h-turnover-event","event_type":"biochemical_relationship","label":"The collagen enzyme can start working without vitamin C, but sustained work needs vitamin C support.","description":"Purified chick collagen prolyl hydroxylase completed approximately 15–30 rapid catalytic cycles in 5–10 seconds without added ascorbate before activity declined.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"00d6f82e-4f52-54ea-9121-c4d332c8cd53","slug":"chick-collagen-prolyl-4-hydroxylase","display_name":"Chick collagen prolyl 4-hydroxylase preparation","entity_type_key":"protein_complex"},"role":"enzyme","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"0cf232e8-346d-54d2-97ee-659df9edaddb","slug":"collagen-proline-residues","display_name":"Collagen-bound proline residues","entity_type_key":"protein_state"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"23ef973a-e863-5779-8379-474dae7cdc5e","slug":"collagen-4-hydroxyproline-residues","display_name":"Collagen-bound 4-hydroxyproline residues","entity_type_key":"protein_state"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""},{"entity":{"id":"38d0c4d9-53d1-5239-bfe3-c1b5e9b79085","slug":"ascorbate","display_name":"L-Ascorbate","entity_type_key":"small_molecule"},"role":"supporting-reductant","stoichiometry":null,"state_label":"","sequence_order":3,"notes":""},{"entity":{"id":"59d6d1cd-df32-5b58-b950-3188bc7b95d6","slug":"iron-ii","display_name":"Ferrous iron","entity_type_key":"ion"},"role":"enzyme-metal-cofactor","stoichiometry":null,"state_label":"","sequence_order":4,"notes":""},{"entity":{"id":"628ddc2d-e4d9-59c7-ae76-0c0cab80a6b1","slug":"2-oxoglutarate","display_name":"2-Oxoglutarate","entity_type_key":"small_molecule"},"role":"cosubstrate","stoichiometry":null,"state_label":"","sequence_order":5,"notes":""},{"entity":{"id":"899c7ab0-6f81-5b38-a6bd-fbb33d66ac8d","slug":"oxygen","display_name":"Molecular oxygen","entity_type_key":"small_molecule"},"role":"cosubstrate","stoichiometry":null,"state_label":"","sequence_order":6,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Purified chick-embryo collagen prolyl hydroxylase kinetics","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Ascorbate omitted or added in purified-enzyme assays; initial 5–10 seconds versus approximately 1 minute.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Purified assay with cofactor omission; does not quantify a dietary requirement or establish an identical turnover number in human cells.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin C research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-c","display_name":"Vitamin C","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Gallus gallus","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The collagen enzyme can start working without vitamin C, but sustained work needs vitamin C support.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[myllyla1978] The role of ascorbate in the prolyl hydroxylase reaction. (1978). https://pubmed.ncbi.nlm.nih.gov/212056/ DOI: 10.1016/0006-291x(78)91010-0","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Chick embryo enzyme preparation","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"2bc0b0c7-683d-5a06-a003-ebd8b380dd30","evidence_kind":"source_excerpt","locator":"Lines 572-583","start_line":572,"end_line":583,"excerpt":"### vc-enzyme-initial-p4h-turnover\nPurified chick collagen prolyl hydroxylase completed approximately 15–30 rapid catalytic cycles in 5–10 seconds without added ascorbate before activity declined.\nCondition category: normal\nnutrient_topic: Vitamin C research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The collagen enzyme can start working without vitamin C, but sustained work needs vitamin C support.\norganism: Gallus gallus\ntissue_or_cell_type: Chick embryo enzyme preparation\nexperimental_model: Purified chick-embryo collagen prolyl hydroxylase kinetics\nlimitations: Purified assay with cofactor omission; does not quantify a dietary requirement or establish an identical turnover number in human cells.\ncross_nutrient: Vitamin C chemistry in collagen, modified-lysine/carnitine metabolism or copper-dependent peptide/catecholamine processing.\nexposure: Ascorbate omitted or added in purified-enzyme assays; initial 5–10 seconds versus approximately 1 minute.\n[myllyla1978] The role of ascorbate in the prolyl hydroxylase reaction. 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