{"id":"f0f4f8bd-95eb-59d1-a039-631ab6ed9bff","stable_key":"31b1baa4-4113-5541-b9e7-fe44a5253a07:ubiad1-mk4","predicate":"decreases_in_recorded_experiment","statement":"Silencing human UBIAD1 reduced labeled-precursor MK-4 biosynthesis.","claim_class":"observational","status":"source_recorded","evidence_grade":"ungraded","direction":"negative","is_public":true,"mechanism_event_id":"322b7d65-c339-5997-a4fb-63a941c1b2b4","mechanism_event_label":"Silencing human UBIAD1 reduced labeled-precursor MK-4 biosynthesis.","subject":{"id":"190c8a9f-60f4-5341-898e-187a0c697624","slug":"ubiad1","display_name":"Human UBIAD1 prenyltransferase","entity_type_key":"protein"},"object":{"id":"c06c54bb-69ce-58a3-a904-0647dbaf3577","slug":"mk4-biosynthesis","display_name":"Menaquinone-4 biosynthesis","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"322b7d65-c339-5997-a4fb-63a941c1b2b4","stable_key":"31b1baa4-4113-5541-b9e7-fe44a5253a07:ubiad1-mk4-event","event_type":"experimental_observation","label":"Silencing human UBIAD1 reduced labeled-precursor MK-4 biosynthesis.","description":"**Fecal vitamin K is not absorbed vitamin K.** In 77 overweight Chinese adults, fecal menaquinone patterns associated with microbial composition. A diet intervention decreased fecal MK-4, MK-6 and MK-8, but longitudinal menaquinone patterns did not associate with glycemia, insulin resistance or inflammation. Separately, human UBIAD1 silencing reduced MK-4 biosynthesis in labeled-precursor experiments; UBIAD1 is a host prenyltransferase, not a shikimate-pathway enzyme. Neither result proves that microbial shikimate output determines tissue vitamin-K adequacy. [Fecal menaquinone profiles of overweight adults are associated with gut microbiota composition during a gut microbiota-targeted dietary intervention.](https://pubmed.ncbi.nlm.nih.gov/26016865/) [Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme.](https://pubmed.ncbi.nlm.nih.gov/20953171/)","status":"provisional","compartment":null,"participants":[{"entity":{"id":"190c8a9f-60f4-5341-898e-187a0c697624","slug":"ubiad1","display_name":"Human UBIAD1 prenyltransferase","entity_type_key":"protein"},"role":"tested factor","stoichiometry":null,"state_label":"UBIAD1 silencing","sequence_order":0,"notes":""},{"entity":{"id":"c06c54bb-69ce-58a3-a904-0647dbaf3577","slug":"mk4-biosynthesis","display_name":"Menaquinone-4 biosynthesis","entity_type_key":"cellular_process"},"role":"measured outcome","stoichiometry":null,"state_label":"decrease","sequence_order":1,"notes":""},{"entity":{"id":"5155b9d1-e835-54b4-9f61-4cf35b3e5227","slug":"menaquinone-4","display_name":"Menaquinone-4 / MK-4 / menatetrenone","entity_type_key":"small_molecule"},"role":"host product","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"availability_state","value_text":"machinery_impairment","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null},{"dimension":"evidence_access","value_text":"Primary indexed abstract reviewed; full results, tables and supplements not independently extracted.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_contrast","value_text":"{\"intervention\": \"UBIAD1 silencing\", \"comparator\": \"Matched functional UBIAD1 background\", \"endpoint\": \"Silencing human UBIAD1 reduced labeled-precursor MK-4 biosynthesis.\", \"effect_direction\": \"decrease\", \"combination\": \"single\", \"conditions\": []}","comparator":null,"unit":null,"notes":"Explicit extracted experimental comparison; source-derived draft.","entity":null},{"dimension":"experimental_model","value_text":"Human cellular gene-silencing and enzyme studies.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"interpretation_status","value_text":"Source-derived extraction of a fact-checked reference; access is explicit, not independent raw-data verification.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Host prenylation route; no human shikimate pathway is implied.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Silencing human UBIAD1 reduced labeled-precursor MK-4 biosynthesis.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Fecal menaquinone profiles of overweight adults are associated with gut microbiota composition during a gut microbiota-targeted dietary intervention. | 2015 | DOI 10.3945/ajcn.115.109496 | PMID 26016865 | https://pubmed.ncbi.nlm.nih.gov/26016865/ | https://doi.org/10.3945/ajcn.115.109496","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme. | 2010 | DOI 10.1038/nature09464 | PMID 20953171 | https://pubmed.ncbi.nlm.nih.gov/20953171/ | https://doi.org/10.1038/nature09464","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"source_locator","value_text":"Reviewed reference lines 31-31; exact primary location described in quoted passage where extracted.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"trigger_kind","value_text":"machinery_impairment","comparator":null,"unit":null,"notes":"Imported condition classification; unverified.","entity":null}],"evidence":[{"id":"5478d97f-91db-596e-88c4-e10b891c3398","evidence_kind":"source_excerpt","locator":"Lines 31-31","start_line":31,"end_line":31,"excerpt":"**Fecal vitamin K is not absorbed vitamin K.** In 77 overweight Chinese adults, fecal menaquinone patterns associated with microbial composition. A diet intervention decreased fecal MK-4, MK-6 and MK-8, but longitudinal menaquinone patterns did not associate with glycemia, insulin resistance or inflammation. Separately, human UBIAD1 silencing reduced MK-4 biosynthesis in labeled-precursor experiments; UBIAD1 is a host prenyltransferase, not a shikimate-pathway enzyme. Neither result proves that microbial shikimate output determines tissue vitamin-K adequacy. [Fecal menaquinone profiles of overweight adults are associated with gut microbiota composition during a gut microbiota-targeted dietary intervention.](https://pubmed.ncbi.nlm.nih.gov/26016865/) [Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme.](https://pubmed.ncbi.nlm.nih.gov/20953171/)","model_system":"Human cellular gene-silencing and enzyme studies.","directness":"reported_statement","verification_status":"source_recorded","notes":"Exact excerpt of the retained AI-assisted reviewed reference; primary sources are cited in primary_references and access scope is retained. 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