Component

1-alpha,25-Dihydroxyvitamin D2

Active 1alpha-hydroxylated D2 hormone; not calcitriol, which denotes the corresponding D3 molecule.

4 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 CYP24A1 initial catalytic efficiency for calcitriol was almost twice that for the active D2 hormone in the matched vesicle experiment.

    1-alpha,25-Dihydroxyvitamin D2 → Calcitriol source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Primary abstract: identified C24R products and comparative initial-rate kinetics.
    experimental_model
    Matched recombinant human CYP24A1 kinetics
    exposure
    Comparison of kcat/Km; low-substrate limit.
    limitations
    This observation does not establish longer in-vivo D2 hormone exposure or negate clinical differences between parent vitamin dosing regimens.
    nutrient
    Vitamin D2 and D3 · Vitamin D2 and D3
    nutrient_topic
    Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin D2 and D3
    organism
    Homo sapiens protein
    plain_language
    Active D2 was initially oxidized more slowly than active D3 in this assay.
    primary_references
    [li2023] Inactivation of vitamin D2 metabolites by human CYP24A1. (2023). https://pubmed.ncbi.nlm.nih.gov/37495192/ DOI: 10.1016/j.jsbmb.2023.106368
    tissue_or_cell_type
    phospholipid-vesicle membrane

    Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 557–570

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Matched recombinant human CYP24A1 kinetics · source_derived_draft · unverified_draft

    ### vd-act-cyp24a1-hormone-selectivity Human CYP24A1 initial catalytic efficiency for calcitriol was almost twice that for the active D2 hormone in the matched vesicle experiment. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Active D2 was initially oxidized more slowly than active D3 in this assay. organism: Homo sapiens protein tissue_or_cell_type: phospholipid-vesicle membrane experimental_model: Matched recombinant human CYP24A1 kinetics limitations: This observation does not establish longer in-vivo D2 hormone exposure or negate clinical differences between parent vitamin dosing regimens. exposure: Comparison of kcat/Km; low-substrate limit. cross_nutrient: false evidence_location: Primary abstract: identified C24R products and comparative initial-rate kinetics. nutrient: Vitamin D2 and D3 [li2023] Inactivation of vitamin D2 metabolites by human CYP24A1. (2023). https://pubmed.ncbi.nlm.nih.gov/37495192/ DOI: 10.1016/j.jsbmb.2023.106368
    Complete structured claim and evidence

What acts on it

  1. Human CYP27B1 1alpha-hydroxylated 25-hydroxyvitamin D2 in phospholipid vesicles; low-substrate catalytic efficiency was similar to that measured for calcifediol.

    Vitamin D 1-alpha-hydroxylase / CYP27B1 → 1-alpha,25-Dihydroxyvitamin D2 source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Primary Tables 3-5, Figure 6A and Experimental procedures; full text retrieved.
    experimental_model
    Partially purified human CYP27B1 membrane assay
    exposure
    5-40 nM CYP27B1; 15 micromolar FDX1, 0.4 micromolar FDXR, 50 micromolar NADPH; 2 min at 37 C. Table 5/Figure 6A.
    limitations
    D2 kinetic data came from one experiment; results do not establish human dosing equivalence.
    nutrient
    Vitamin D2 and D3 · Vitamin D2 and D3
    nutrient_topic
    Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin D2 and D3
    organism
    Homo sapiens proteins
    plain_language
    CYP27B1 completes activation of the D2 precursor.
    primary_references
    [tang2012] Expression of human CYP27B1 in Escherichia coli and characterization in phospholipid vesicles. (2012). https://pubmed.ncbi.nlm.nih.gov/22862690/ DOI: 10.1111/j.1742-4658.2012.08736.x
    tissue_or_cell_type
    reconstituted inner-mitochondrial-membrane model

    Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 437–450

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Partially purified human CYP27B1 membrane assay · source_derived_draft · unverified_draft

    ### vd-act-cyp27b1-d2 Human CYP27B1 1alpha-hydroxylated 25-hydroxyvitamin D2 in phospholipid vesicles; low-substrate catalytic efficiency was similar to that measured for calcifediol. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: CYP27B1 completes activation of the D2 precursor. organism: Homo sapiens proteins tissue_or_cell_type: reconstituted inner-mitochondrial-membrane model experimental_model: Partially purified human CYP27B1 membrane assay limitations: D2 kinetic data came from one experiment; results do not establish human dosing equivalence. exposure: 5-40 nM CYP27B1; 15 micromolar FDX1, 0.4 micromolar FDXR, 50 micromolar NADPH; 2 min at 37 C. Table 5/Figure 6A. cross_nutrient: false evidence_location: Primary Tables 3-5, Figure 6A and Experimental procedures; full text retrieved. nutrient: Vitamin D2 and D3 [tang2012] Expression of human CYP27B1 in Escherichia coli and characterization in phospholipid vesicles. (2012). https://pubmed.ncbi.nlm.nih.gov/22862690/ DOI: 10.1111/j.1742-4658.2012.08736.x
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Human CYP24A1 initiated active 1alpha,25-dihydroxyvitamin D2 oxidation through C24R hydroxylation.

    Vitamin D 24-hydroxylase / CYP24A1 → 1-alpha,24R,25-Trihydroxyvitamin D2 source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Primary abstract: identified C24R products and comparative initial-rate kinetics.
    experimental_model
    Partially purified human CYP24A1 product analysis
    exposure
    1,25(OH)2D2 substrate; concentration/time not specified in abstract.
    limitations
    Product profile is human enzyme-specific; active D2 is not calcitriol.
    nutrient
    Vitamin D2 and D3 · Vitamin D2 and D3
    nutrient_topic
    Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin D2 and D3
    organism
    Homo sapiens protein
    plain_language
    CYP24A1 also starts breaking down the active D2 hormone.
    primary_references
    [li2023] Inactivation of vitamin D2 metabolites by human CYP24A1. (2023). https://pubmed.ncbi.nlm.nih.gov/37495192/ DOI: 10.1016/j.jsbmb.2023.106368
    tissue_or_cell_type
    phospholipid-vesicle membrane

    Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 527–540

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Partially purified human CYP24A1 product analysis · source_derived_draft · unverified_draft

    ### vd-act-cyp24a1-active-d2 Human CYP24A1 initiated active 1alpha,25-dihydroxyvitamin D2 oxidation through C24R hydroxylation. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: CYP24A1 also starts breaking down the active D2 hormone. organism: Homo sapiens protein tissue_or_cell_type: phospholipid-vesicle membrane experimental_model: Partially purified human CYP24A1 product analysis limitations: Product profile is human enzyme-specific; active D2 is not calcitriol. exposure: 1,25(OH)2D2 substrate; concentration/time not specified in abstract. cross_nutrient: false evidence_location: Primary abstract: identified C24R products and comparative initial-rate kinetics. nutrient: Vitamin D2 and D3 [li2023] Inactivation of vitamin D2 metabolites by human CYP24A1. (2023). https://pubmed.ncbi.nlm.nih.gov/37495192/ DOI: 10.1016/j.jsbmb.2023.106368
    Complete structured claim and evidence

  2. Purified rat CYP24A1 produced a C24R-hydroxylated metabolite from active D2 but no detectable calcitroic acid under conditions that generated calcitroic acid from calcitriol.

    Rat vitamin D 24-hydroxylase / Cyp24a1 → Calcitroic acid source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    evidence_location
    Primary abstract, purified-enzyme HPLC results.
    experimental_model
    Purified rat CYP24A1 with HPLC product analysis
    exposure
    Active D2 versus D3 substrates; detailed dose/time unavailable in abstract.
    limitations
    Negative detection is assay-specific. Rat enzyme behavior is not a claim that humans cannot metabolize D2 further.
    nutrient
    Vitamin D2 and D3 · Vitamin D2 and D3
    nutrient_topic
    Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin D2 and D3
    organism
    Rattus norvegicus protein
    plain_language
    A rat enzyme experiment found different terminal breakdown products for D2 and D3.
    primary_references
    [horst2003] Rat cytochrome P450C24 (CYP24) does not metabolize 1,25-dihydroxyvitamin D2 to calcitroic acid. (2003). https://pubmed.ncbi.nlm.nih.gov/12520527/ DOI: 10.1002/jcb.10359
    tissue_or_cell_type
    cell-free enzyme system

    Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 572–585

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified rat CYP24A1 with HPLC product analysis · source_derived_draft · unverified_draft

    ### vd-act-rat-cyp24-d2-boundary Purified rat CYP24A1 produced a C24R-hydroxylated metabolite from active D2 but no detectable calcitroic acid under conditions that generated calcitroic acid from calcitriol. Condition category: normal nutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect. plain_language: A rat enzyme experiment found different terminal breakdown products for D2 and D3. organism: Rattus norvegicus protein tissue_or_cell_type: cell-free enzyme system experimental_model: Purified rat CYP24A1 with HPLC product analysis limitations: Negative detection is assay-specific. Rat enzyme behavior is not a claim that humans cannot metabolize D2 further. exposure: Active D2 versus D3 substrates; detailed dose/time unavailable in abstract. cross_nutrient: false evidence_location: Primary abstract, purified-enzyme HPLC results. nutrient: Vitamin D2 and D3 [horst2003] Rat cytochrome P450C24 (CYP24) does not metabolize 1,25-dihydroxyvitamin D2 to calcitroic acid. (2003). https://pubmed.ncbi.nlm.nih.gov/12520527/ DOI: 10.1002/jcb.10359
    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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