Component

Human tryptophan 2,3-dioxygenase / TDO2

Human heme-containing enzyme initiating tryptophan oxidative cleavage.

3 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What it acts on

  1. Human TDO2 substrate and product structures support oxidative conversion of L-tryptophan and oxygen to N-formylkynurenine.

    Human tryptophan 2,3-dioxygenase / TDO2 → N-Formyl-L-kynurenine source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    Tryptophan provides the carbon framework entering the de novo niacin pathway; downstream steps remain necessary.
    evidence_span
    {"source_cache": "artifacts/niacin-precursors-sources/tdo2016.paragraphs.txt", "locator": "Normalized full-text paragraphs 9–9 (0-based)", "start_char": 8003, "end_char": 9136, "file_sha256": "3f91886745b8ff9fb808232c839dd346b03605dd025d5fa682a3de4f81338ec5", "text_sha256": "b39e2ce5d405e5eb8fde25aec369c306954365d7ec2b448fe5a5689e89785e2a"}
    experimental_model
    Purified human TDO2 crystallography and spectroscopy; substrate/product complexes
    exposure
    Biochemical or structural assay; no dietary intervention
    limitations
    Purified-enzyme evidence does not establish dietary intake requirements or clinical outcomes.
    nutrient_topic
    Niacin research collection; topical membership is not evidence of a direct dietary effect. · Niacin (vitamin B3)
    organism
    Homo sapiens
    plain_language
    TDO2 opens the tryptophan ring at the beginning of the kynurenine route.
    primary_references
    [b3-pre-tdo2016] Molecular basis for catalysis and substrate-mediated cellular stabilization of human tryptophan 2,3-dioxygenase. (2016). https://pubmed.ncbi.nlm.nih.gov/27762317/ DOI: 10.1038/srep35169
    tissue_or_cell_type
    Purified recombinant protein; no intact tissue

    Niacin: NAD metabolism, deficiency and nutrient interactions (2026-09-17) · lines 479–491

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human TDO2 crystallography and spectroscopy; substrate/product complexes · source_derived_draft · unverified_draft

    ### b3-pre-tdo-reaction Human TDO2 substrate and product structures support oxidative conversion of L-tryptophan and oxygen to N-formylkynurenine. Condition category: normal nutrient_topic: Niacin research collection; topical membership is not evidence of a direct dietary effect. plain_language: TDO2 opens the tryptophan ring at the beginning of the kynurenine route. organism: Homo sapiens tissue_or_cell_type: Purified recombinant protein; no intact tissue experimental_model: Purified human TDO2 crystallography and spectroscopy; substrate/product complexes limitations: Purified-enzyme evidence does not establish dietary intake requirements or clinical outcomes. exposure: Biochemical or structural assay; no dietary intervention cross_nutrient: Tryptophan provides the carbon framework entering the de novo niacin pathway; downstream steps remain necessary. evidence_span: {"source_cache": "artifacts/niacin-precursors-sources/tdo2016.paragraphs.txt", "locator": "Normalized full-text paragraphs 9–9 (0-based)", "start_char": 8003, "end_char": 9136, "file_sha256": "3f91886745b8ff9fb808232c839dd346b03605dd025d5fa682a3de4f81338ec5", "text_sha256": "b39e2ce5d405e5eb8fde25aec369c306954365d7ec2b448fe5a5689e89785e2a"} [b3-pre-tdo2016] Molecular basis for catalysis and substrate-mediated cellular stabilization of human tryptophan 2,3-dioxygenase. (2016). https://pubmed.ncbi.nlm.nih.gov/27762317/ DOI: 10.1038/srep35169
    Complete structured claim and evidence

What acts on it

  1. In the human TDO2 substrate complex, molecular oxygen was coordinated to the heme iron next to the L-tryptophan substrate.

    Heme → Human tryptophan 2,3-dioxygenase / TDO2 source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    Heme iron participates in a tryptophan-to-niacin upstream enzyme; the structure does not establish a dietary iron threshold.
    evidence_span
    {"source_cache": "artifacts/niacin-precursors-sources/tdo2016.paragraphs.txt", "locator": "Normalized full-text paragraphs 7–7 (0-based)", "start_char": 5512, "end_char": 7250, "file_sha256": "3f91886745b8ff9fb808232c839dd346b03605dd025d5fa682a3de4f81338ec5", "text_sha256": "057137936657c739cdef730f5d10b930ec40af5e09f0ed4e2abbd813f26db9f0"}
    experimental_model
    Purified human TDO2 crystallography and spectroscopy; substrate/product complexes
    exposure
    Biochemical or structural assay; no dietary intervention
    limitations
    Purified-enzyme evidence does not establish dietary intake requirements or clinical outcomes.
    nutrient_topic
    Niacin research collection; topical membership is not evidence of a direct dietary effect. · Niacin (vitamin B3)
    organism
    Homo sapiens
    plain_language
    Iron held in heme positions oxygen for this precursor reaction.
    primary_references
    [b3-pre-tdo2016] Molecular basis for catalysis and substrate-mediated cellular stabilization of human tryptophan 2,3-dioxygenase. (2016). https://pubmed.ncbi.nlm.nih.gov/27762317/ DOI: 10.1038/srep35169
    tissue_or_cell_type
    Purified recombinant protein; no intact tissue

    Niacin: NAD metabolism, deficiency and nutrient interactions (2026-09-17) · lines 493–505

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human TDO2 crystallography and spectroscopy; substrate/product complexes · source_derived_draft · unverified_draft

    ### b3-pre-tdo-heme-oxygen In the human TDO2 substrate complex, molecular oxygen was coordinated to the heme iron next to the L-tryptophan substrate. Condition category: normal nutrient_topic: Niacin research collection; topical membership is not evidence of a direct dietary effect. plain_language: Iron held in heme positions oxygen for this precursor reaction. organism: Homo sapiens tissue_or_cell_type: Purified recombinant protein; no intact tissue experimental_model: Purified human TDO2 crystallography and spectroscopy; substrate/product complexes limitations: Purified-enzyme evidence does not establish dietary intake requirements or clinical outcomes. exposure: Biochemical or structural assay; no dietary intervention cross_nutrient: Heme iron participates in a tryptophan-to-niacin upstream enzyme; the structure does not establish a dietary iron threshold. evidence_span: {"source_cache": "artifacts/niacin-precursors-sources/tdo2016.paragraphs.txt", "locator": "Normalized full-text paragraphs 7–7 (0-based)", "start_char": 5512, "end_char": 7250, "file_sha256": "3f91886745b8ff9fb808232c839dd346b03605dd025d5fa682a3de4f81338ec5", "text_sha256": "057137936657c739cdef730f5d10b930ec40af5e09f0ed4e2abbd813f26db9f0"} [b3-pre-tdo2016] Molecular basis for catalysis and substrate-mediated cellular stabilization of human tryptophan 2,3-dioxygenase. (2016). https://pubmed.ncbi.nlm.nih.gov/27762317/ DOI: 10.1038/srep35169
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Human tumor-cell TDO-derived kynurenine supported AHR-dependent survival and motility in the study.

    L-Kynurenine → Human aryl hydrocarbon receptor / AHR source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human tumor-cell experiments with human brain-tumor associations.
    limitations
    The chemical identity of the active ligand requires care: later work identified potent trace kynurenine condensation products.
    nutrient_topic
    Tryptophan collection; molecular form, preparation, species, exposure and manipulation remain explicit. · L-Tryptophan
    plain_language
    The catabolic route could feed a tumor-associated signal.
    primary_references
    An endogenous tumour-promoting ligand of the human aryl hydrocarbon receptor. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21976023/ · DOI 10.1038/nature10491

    Tryptophan: transport, protein synthesis, neuroactive metabolites, NAD and microbial pathways (2026-09-19) · lines 426–432

    AI-assisted research curation; primary-abstract references and experimental limitations individually identified. Not publisher full text. · supports · Human tumor-cell experiments with human brain-tumor associations. · source_derived_draft · unverified_draft

    ## tryptophan-tdo-ahr The catabolic route could feed a tumor-associated signal. Human tumor-cell TDO-derived kynurenine supported AHR-dependent survival and motility in the study. Model: Human tumor-cell experiments with human brain-tumor associations. Limitations: The chemical identity of the active ligand requires care: later work identified potent trace kynurenine condensation products. Evidence access: Primary abstract An endogenous tumour-promoting ligand of the human aryl hydrocarbon receptor. · 2011 · https://pubmed.ncbi.nlm.nih.gov/21976023/ · DOI 10.1038/nature10491
    Complete structured claim and evidence

In the sources

Preserved passages that mention this component, quoted exactly. Open one to read it in context.

    This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.

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