{"id":"c7cd75b7-3737-5a54-8a40-65f3c472a825","stable_key":"31b1baa4-4113-5541-b9e7-fe44a5253a07:paba-folate","predicate":"reported_relationship","statement":"pABA is a bacterial folate biosynthetic precursor downstream of the chorismate/PabC branch.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"neutral","is_public":true,"mechanism_event_id":"34350213-acce-53df-811c-16385b656ebf","mechanism_event_label":"pABA is a bacterial folate biosynthetic precursor downstream of the chorismate/PabC branch.","subject":{"id":"eef4779e-36ce-504c-be2c-a72bdb64f22d","slug":"4-aminobenzoate","display_name":"4-Aminobenzoate / pABA","entity_type_key":"small_molecule"},"object":{"id":"e176a266-711e-5469-89da-3fb2d3f244ad","slug":"folate","display_name":"Folate (vitamin B9)","entity_type_key":"chemical_species"},"evidence_count":1,"mechanism_event":{"id":"34350213-acce-53df-811c-16385b656ebf","stable_key":"31b1baa4-4113-5541-b9e7-fe44a5253a07:paba-folate-event","event_type":"biochemical_relationship","label":"pABA is a bacterial folate biosynthetic precursor downstream of the chorismate/PabC branch.","description":"**The folate branch contains a B6-dependent step.** In E. coli, PabA supplies nitrogen from glutamine, generating glutamate; PabB uses chorismate and that nitrogen to form 4-amino-4-deoxychorismate. PabC then cleaves this intermediate to p-aminobenzoate (pABA) and pyruvate. The purified PabC enzyme contains pyridoxal phosphate (PLP), a B6 cofactor. A disrupted pabC strain required external pABA for growth. This establishes a microbial cofactor and biosynthetic dependency, not that marginal human B6 deficiency causes microbial folate failure. pABA is a precursor used in bacterial folate synthesis, not folate itself. [para-aminobenzoate synthesis from chorismate occurs in two steps.](https://pubmed.ncbi.nlm.nih.gov/2656685/) [Characterization and sequence of Escherichia coli pabC, the gene encoding aminodeoxychorismate lyase, a pyridoxal phosphate-containing enzyme.](https://pubmed.ncbi.nlm.nih.gov/1644759/)","status":"provisional","compartment":null,"participants":[{"entity":{"id":"eef4779e-36ce-504c-be2c-a72bdb64f22d","slug":"4-aminobenzoate","display_name":"4-Aminobenzoate / pABA","entity_type_key":"small_molecule"},"role":"tested factor","stoichiometry":null,"state_label":"as reported","sequence_order":0,"notes":""},{"entity":{"id":"e176a266-711e-5469-89da-3fb2d3f244ad","slug":"folate","display_name":"Folate (vitamin B9)","entity_type_key":"chemical_species"},"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 biosynthesis context, not mammalian de-novo folate synthesis.","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":"Multistep branch relationship; not direct pABA-to-folate conversion, increased human plasma folate or a supplement effect.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"pABA is a bacterial folate biosynthetic precursor downstream of the chorismate/PabC branch.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Characterization and sequence of Escherichia coli pabC, the gene encoding aminodeoxychorismate lyase, a pyridoxal phosphate-containing enzyme. | 1992 | DOI 10.1128/jb.174.16.5317-5323.1992 | PMID 1644759 | https://pubmed.ncbi.nlm.nih.gov/1644759/ | https://doi.org/10.1128/jb.174.16.5317-5323.1992 | https://pmc.ncbi.nlm.nih.gov/articles/PMC206368/","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"para-aminobenzoate synthesis from chorismate occurs in two steps. | 1989 | DOI 10.1016/s0021-9258(18)81833-6 | PMID 2656685 | https://pubmed.ncbi.nlm.nih.gov/2656685/ | https://doi.org/10.1016/s0021-9258(18)81833-6","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"source_locator","value_text":"Reviewed reference lines 25-25; exact primary location described in quoted passage where extracted.","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"d975f3cd-e643-57a4-8935-172a85157af5","evidence_kind":"source_excerpt","locator":"Lines 25-25","start_line":25,"end_line":25,"excerpt":"**The folate branch contains a B6-dependent step.** In E. coli, PabA supplies nitrogen from glutamine, generating glutamate; PabB uses chorismate and that nitrogen to form 4-amino-4-deoxychorismate. PabC then cleaves this intermediate to p-aminobenzoate (pABA) and pyruvate. The purified PabC enzyme contains pyridoxal phosphate (PLP), a B6 cofactor. A disrupted pabC strain required external pABA for growth. This establishes a microbial cofactor and biosynthetic dependency, not that marginal human B6 deficiency causes microbial folate failure. pABA is a precursor used in bacterial folate synthesis, not folate itself. [para-aminobenzoate synthesis from chorismate occurs in two steps.](https://pubmed.ncbi.nlm.nih.gov/2656685/) [Characterization and sequence of Escherichia coli pabC, the gene encoding aminodeoxychorismate lyase, a pyridoxal phosphate-containing enzyme.](https://pubmed.ncbi.nlm.nih.gov/1644759/)","model_system":"E. coli biosynthesis context, not mammalian de-novo folate synthesis.","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}