{"id":"bb8f8e33-8b97-5fd4-ac96-5fcba21b8bd5","stable_key":"31b1baa4-4113-5541-b9e7-fe44a5253a07:mk8-label-shikimate","predicate":"reported_relationship","statement":"Isotope-labeled shikimate contributed carbon to E. coli MK-8 in the historical labeling experiment.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"neutral","is_public":true,"mechanism_event_id":"27cfcb50-efee-5cc4-a091-ed573282e784","mechanism_event_label":"Isotope-labeled shikimate contributed carbon to E. coli MK-8 in the historical labeling experiment.","subject":{"id":"fe7a4dc3-4f06-586b-9457-2dd949e2fa36","slug":"shikimate","display_name":"Shikimate anion","entity_type_key":"small_molecule"},"object":{"id":"40a1397b-e0d8-5c2a-916a-52ae778c4e11","slug":"menaquinone-8","display_name":"Menaquinone-8 / MK-8","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"27cfcb50-efee-5cc4-a091-ed573282e784","stable_key":"31b1baa4-4113-5541-b9e7-fe44a5253a07:mk8-label-shikimate-event","event_type":"biochemical_relationship","label":"Isotope-labeled shikimate contributed carbon to E. coli MK-8 in the historical labeling experiment.","description":"**The K and Q branches are organism-specific.** Isotope experiments in E. coli traced shikimate carbon into the benzene ring of menaquinone-8 (MK-8), and methionine-derived methyl carbon into that product. This does not establish increased human MK-7, vitamin-K function or an oral shikimate dose response. Separately, an E. coli ubiC mutant failed to convert chorismate to 4-hydroxybenzoate and produced little ubiquinone unless supplied with 4-hydroxybenzoate. UbiC therefore identifies a branch-specific supply bottleneck; bacterial ubiquinone production is not synonymous with human mitochondrial CoQ10 synthesis. [The role of shikimic acid in the biosynthesis of vitamin K2.](https://pubmed.ncbi.nlm.nih.gov/5337721/) [Biosynthesis of ubiquinone in Escherichia coli K-12: biochemical and genetic characterization of a mutant unable to convert chorismate into 4-hydroxybenzoate.](https://pubmed.ncbi.nlm.nih.gov/4595202/)","status":"provisional","compartment":null,"participants":[{"entity":{"id":"fe7a4dc3-4f06-586b-9457-2dd949e2fa36","slug":"shikimate","display_name":"Shikimate anion","entity_type_key":"small_molecule"},"role":"tested factor","stoichiometry":null,"state_label":"as reported","sequence_order":0,"notes":""},{"entity":{"id":"40a1397b-e0d8-5c2a-916a-52ae778c4e11","slug":"menaquinone-8","display_name":"Menaquinone-8 / MK-8","entity_type_key":"small_molecule"},"role":"measured outcome","stoichiometry":null,"state_label":"not_reported","sequence_order":1,"notes":""}]},"contexts":[{"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_model","value_text":"E. coli 1966 isotope tracing; shikimate ring carbon versus methionine methyl carbon.","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":"Carbon incorporation, not complete enzymatic sequence, human MK-7 production or oral vitamin-K efficacy.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Isotope-labeled shikimate contributed carbon to E. coli MK-8 in the historical labeling experiment.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Biosynthesis of ubiquinone in Escherichia coli K-12: biochemical and genetic characterization of a mutant unable to convert chorismate into 4-hydroxybenzoate. | 1974 | DOI 10.1128/jb.118.1.41-45.1974 | PMID 4595202 | https://pubmed.ncbi.nlm.nih.gov/4595202/ | https://doi.org/10.1128/jb.118.1.41-45.1974 | https://pmc.ncbi.nlm.nih.gov/articles/PMC246637/","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"The role of shikimic acid in the biosynthesis of vitamin K2. | 1966 | DOI 10.1042/bj1000001 | PMID 5337721 | https://pubmed.ncbi.nlm.nih.gov/5337721/ | https://doi.org/10.1042/bj1000001 | https://pmc.ncbi.nlm.nih.gov/articles/PMC1265084/","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"source_locator","value_text":"Reviewed reference lines 27-27; exact primary location described in quoted passage where extracted.","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"77590415-d586-5c05-8b71-90894543e4b1","evidence_kind":"source_excerpt","locator":"Lines 27-27","start_line":27,"end_line":27,"excerpt":"**The K and Q branches are organism-specific.** Isotope experiments in E. coli traced shikimate carbon into the benzene ring of menaquinone-8 (MK-8), and methionine-derived methyl carbon into that product. This does not establish increased human MK-7, vitamin-K function or an oral shikimate dose response. Separately, an E. coli ubiC mutant failed to convert chorismate to 4-hydroxybenzoate and produced little ubiquinone unless supplied with 4-hydroxybenzoate. UbiC therefore identifies a branch-specific supply bottleneck; bacterial ubiquinone production is not synonymous with human mitochondrial CoQ10 synthesis. [The role of shikimic acid in the biosynthesis of vitamin K2.](https://pubmed.ncbi.nlm.nih.gov/5337721/) [Biosynthesis of ubiquinone in Escherichia coli K-12: biochemical and genetic characterization of a mutant unable to convert chorismate into 4-hydroxybenzoate.](https://pubmed.ncbi.nlm.nih.gov/4595202/)","model_system":"E. coli 1966 isotope tracing; shikimate ring carbon versus methionine methyl carbon.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Exact excerpt of the retained AI-assisted reviewed reference; primary sources are cited in primary_references and access scope is retained. Not a verbatim quotation from a primary paper.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"e6ae59de-0369-5c2f-8262-57d91302671c","stable_key":"import-31b1baa4-4113-5541-b9e7-fe44a5253a07","title":"Shikimic acid: detailed mechanisms of action (reviewed 5 October 2026)","document_type":"imported_text","citation_label":"Original AI-assisted review of primary studies and, where relevant, official regulatory records. Access level is retained per claim. Corrections, null results and unresolved questions remain explicit. Not publisher full text or independent replication.","file_path":"","sha256":"95b1f9e9577661312d67f36e156d2e49326b207f296c1c0e801a5b007fd8e283","revision_id":"cd3237f1-131a-557d-84b5-7543259807b0","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}