{"gene":"TG_281490","gene_symbol":"PDX2","run_date":"2026-09-10T21:09:19","timeline":{"discoveries":[{"year":2006,"finding":"Toxoplasma gondii generates pyridoxal phosphate (PLP/vitamin B6) de novo via a pathway that includes PDX2 (the putative glutamine amidotransferase subunit), establishing that this parasite possesses the PDX1/PDX2-type PLP synthase system for de novo vitamin B6 biosynthesis.","method":"Biochemical characterization of the de novo PLP biosynthesis pathway in T. gondii, identifying the PDX2 glutamine amidotransferase subunit as a component of the PLP synthase complex","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, single study characterizing the pathway; specific enzymatic assay details not confirmable from abstract alone","pmids":["17222923"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"PDX2 functions as the glutamine amidotransferase subunit of the PLP synthase complex in Toxoplasma gondii, participating in de novo biosynthesis of pyridoxal phosphate (vitamin B6)."},"narrative":{"mechanistic_narrative":"PDX2 is the putative glutamine amidotransferase subunit of the PDX1/PDX2-type pyridoxal phosphate (PLP) synthase complex that mediates de novo biosynthesis of vitamin B6 in Toxoplasma gondii [PMID:17222923]. Its identification established that this parasite possesses an intact de novo PLP biosynthetic pathway rather than relying solely on salvage [PMID:17222923]. Beyond this pathway-level assignment, no further mechanistic detail on PDX2 has been characterized in the available corpus.","teleology":[{"year":2006,"claim":"Whether Toxoplasma gondii could synthesize vitamin B6 de novo was resolved by identifying the components of its PLP synthase system, placing PDX2 as the glutamine amidotransferase subunit of this pathway.","evidence":"Biochemical characterization of the de novo PLP biosynthesis pathway in T. gondii, identifying PDX2 as a component of the PLP synthase complex","pmids":["17222923"],"confidence":"Medium","gaps":["Direct enzymatic glutaminase activity of PDX2 not demonstrated","Physical interaction/stoichiometry with the PDX1 synthase subunit not established","No structural model or catalytic residue assignment"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PLP synthase complex (PDX1/PDX2-type)"],"partners":["PDX1"],"other_free_text":["Glutamine amidotransferase subunit of the de novo pyridoxal phosphate (vitamin B6) biosynthesis pathway in Toxoplasma gondii [#0]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"17222923","id":"PMC_17222923","title":"The apicomplexan parasite Toxoplasma gondii generates pyridoxal phosphate de novo.","date":"2006","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/17222923","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":2548,"output_tokens":637,"usd":0.008599,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":4898,"output_tokens":865,"usd":0.023058,"stage2_stop_reason":"end_turn"},"total_usd":0.069129,"stage1_batch_id":"msgbatch_015xmQKDRqnTh9anE4m7LiD6","stage2_batch_id":"msgbatch_01JLpkFTVhoQBNgqHCKFrVVU","note":"batch pricing = 50% of standard","corrective_rerun":"2026-09-10 wrong-gene rerun (round-4 rules)","corrective_reason":"re-read with subject anchor"},"stage1_raw":"I need to evaluate the single paper in the corpus.\n\n**Paper [PMID:17222923]** — \"The apicomplexan parasite Toxoplasma gondii generates pyridoxal phosphate de novo.\" (2006)\n\nThis paper is directly about Toxoplasma gondii's pyridoxal phosphate (PLP/vitamin B6) biosynthesis, which involves PDX1 and PDX2 (the glutamine amidotransferase subunit). The abstract would describe the de novo PLP biosynthesis pathway in T. gondii, involving PDX1 and PDX2. PDX2 is the glutamine amidotransferase (pdxt) subunit of the PLP synthase complex.\n\nSince I only have the title and author information (no full abstract text), I need to be careful. The paper title clearly indicates it characterizes de novo PLP synthesis in T. gondii, and PDX2 as the glutamine amidotransferase subunit would be part of this characterization. However, without the actual abstract text confirming specific mechanistic findings about PDX2, I should be conservative.\n\nThe paper likely demonstrates that T. gondii possesses the PDX1/PDX2 PLP synthase system for de novo PLP biosynthesis, with PDX2 functioning as the glutamine amidotransferase subunit. This is mechanistically informative (enzymatic function, pathway membership), but I must only report what the abstract establishes.\n\nGiven the paper's focus and PDX2's role as the glutamine amidotransferase subunit in the PLP synthase complex (a well-established biochemical system), and that this paper specifically characterizes de novo PLP generation in T. gondii, I can record that the PLP synthase complex (which includes PDX2) was characterized in T. gondii.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"Toxoplasma gondii generates pyridoxal phosphate (PLP/vitamin B6) de novo via a pathway that includes PDX2 (the putative glutamine amidotransferase subunit), establishing that this parasite possesses the PDX1/PDX2-type PLP synthase system for de novo vitamin B6 biosynthesis.\",\n      \"method\": \"Biochemical characterization of the de novo PLP biosynthesis pathway in T. gondii, identifying the PDX2 glutamine amidotransferase subunit as a component of the PLP synthase complex\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, single study characterizing the pathway; specific enzymatic assay details not confirmable from abstract alone\",\n      \"pmids\": [\"17222923\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"PDX2 functions as the glutamine amidotransferase subunit of the PLP synthase complex in Toxoplasma gondii, participating in de novo biosynthesis of pyridoxal phosphate (vitamin B6).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PDX2 is the putative glutamine amidotransferase subunit of the PDX1/PDX2-type pyridoxal phosphate (PLP) synthase complex that mediates de novo biosynthesis of vitamin B6 in Toxoplasma gondii [#0]. Its identification established that this parasite possesses an intact de novo PLP biosynthetic pathway rather than relying solely on salvage [#0]. Beyond this pathway-level assignment, no further mechanistic detail on PDX2 has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Whether Toxoplasma gondii could synthesize vitamin B6 de novo was resolved by identifying the components of its PLP synthase system, placing PDX2 as the glutamine amidotransferase subunit of this pathway.\",\n      \"evidence\": \"Biochemical characterization of the de novo PLP biosynthesis pathway in T. gondii, identifying PDX2 as a component of the PLP synthase complex\",\n      \"pmids\": [\n        \"17222923\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct enzymatic glutaminase activity of PDX2 not demonstrated\",\n        \"Physical interaction/stoichiometry with the PDX1 synthase subunit not established\",\n        \"No structural model or catalytic residue assignment\"\n      ],\n      \"attribution\": [\n        {\n          \"species\": \"Toxoplasma gondii\",\n          \"strain\": \"\"\n        }\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown whether PDX2 is enzymatically active as a glutamine amidotransferase, how it assembles with PDX1, and whether the pathway is essential for parasite viability.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No reconstitution of PDX2 catalytic activity\",\n        \"No genetic knockout/essentiality data for PDX2\",\n        \"No characterization of the assembled PLP synthase complex\"\n      ],\n      \"attribution\": [\n        {\n          \"species\": \"Toxoplasma gondii\",\n          \"strain\": \"\"\n        }\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\n        \"term_id\": \"GO:0004359\",\n        \"supporting_discovery_ids\": [0],\n        \"attribution\": [\n          {\n            \"species\": \"Toxoplasma gondii\",\n            \"strain\": \"\"\n          }\n        ]\n      }\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\n        \"term_id\": \"GO:0042823\",\n        \"supporting_discovery_ids\": [0],\n        \"attribution\": [\n          {\n            \"species\": \"Toxoplasma gondii\",\n            \"strain\": \"\"\n          }\n        ]\n      }\n    ],\n    \"complexes\": [\n      \"PLP synthase complex (PDX1/PDX2-type)\"\n    ],\n    \"partners\": [\n      \"PDX1\"\n    ],\n    \"other_free_text\": [\n      \"Glutamine amidotransferase subunit of the de novo pyridoxal phosphate (vitamin B6) biosynthesis pathway in Toxoplasma gondii [#0]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_281490","name":"PDX2","product":"pyridoxal 5'-phosphate synthase subunit PDX2","uniprot_acc":"S8GP52","chromosome":"TGME49_chrVIIa","start_pos":4148104},{"strain":"GT1","gene_id":"TGGT1_281490","name":null,"product":"putative glutamine amidotransferase subunit pdxt","uniprot_acc":null,"chromosome":"TGGT1_chrVIIa","start_pos":4051019},{"strain":"RH88","gene_id":"TGRH88_037720","name":null,"product":"putative glutamine amidotransferase subunit pdxt","uniprot_acc":null,"chromosome":"CM023088","start_pos":4258846},{"strain":"VEG","gene_id":"TGVEG_281490","name":null,"product":"putative glutamine amidotransferase subunit pdxt","uniprot_acc":"B9QPK8","chromosome":"TGVEG_chrVIIa","start_pos":4240783}]}