Component

Human transcobalamin / TCN2

Human transcobalamin / TCN2

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

Where it participates (unsigned role)

  1. The human receptor identified as CD320 binds transcobalamin-cobalamin at the plasma membrane and internalizes the carrier-vitamin complex by endocytosis.

    Human transcobalamin receptor / CD320 → Cellular uptake of transcobalamin-bound cobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    Human receptor identification and functional characterization
    exposure
    TC-cobalamin complex presented to receptor
    limitations
    No universal uptake rate, tissue sufficiency threshold, or assertion that this is the sole B12 entry route.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    CD320 brings carrier-bound B12 into cells.
    primary_references
    [quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949
    tissue_or_cell_type
    Plasma-membrane endocytosis

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 374–385

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human receptor identification and functional characterization · source_derived_draft · unverified_draft

    ### b12-abs-cd320-cellular-delivery The human receptor identified as CD320 binds transcobalamin-cobalamin at the plasma membrane and internalizes the carrier-vitamin complex by endocytosis. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: CD320 brings carrier-bound B12 into cells. organism: Homo sapiens tissue_or_cell_type: Plasma-membrane endocytosis experimental_model: Human receptor identification and functional characterization limitations: No universal uptake rate, tissue sufficiency threshold, or assertion that this is the sole B12 entry route. exposure: TC-cobalamin complex presented to receptor cross_nutrient: false [quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949
    Complete structured claim and evidence

  2. Purified human placental receptor and recombinant CD320 extracellular domain bound transcobalamin-cobalamin; high-affinity binding did not require the cytoplasmic domain or membrane orientation.

    Human transcobalamin receptor / CD320 → Human transcobalamin-cobalamin complex source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    Human placental protein purification and recombinant receptor-domain analysis
    exposure
    Holo-TC binding to native or recombinant CD320
    limitations
    Binding-domain result does not show the cytoplasmic tail is dispensable for endocytosis.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    The outside portion of CD320 recognizes B12-loaded transcobalamin.
    primary_references
    [quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949
    tissue_or_cell_type
    Placental plasma membrane/extracellular receptor domain

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 361–372

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Human placental protein purification and recombinant receptor-domain analysis · source_derived_draft · unverified_draft

    ### b12-abs-cd320-holo-binding Purified human placental receptor and recombinant CD320 extracellular domain bound transcobalamin-cobalamin; high-affinity binding did not require the cytoplasmic domain or membrane orientation. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: The outside portion of CD320 recognizes B12-loaded transcobalamin. organism: Homo sapiens tissue_or_cell_type: Placental plasma membrane/extracellular receptor domain experimental_model: Human placental protein purification and recombinant receptor-domain analysis limitations: Binding-domain result does not show the cytoplasmic tail is dispensable for endocytosis. exposure: Holo-TC binding to native or recombinant CD320 cross_nutrient: false [quadros-2009-cd320] The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin. (2009). https://pubmed.ncbi.nlm.nih.gov/18779389/ DOI: 10.1182/blood-2008-05-158949
    Complete structured claim and evidence

  3. Two infant siblings with demonstrated transcobalamin II deficiency developed megaloblastic anemia and systemic B12-deficiency manifestations at three and five weeks despite normal total serum B12.

    Human inherited transcobalamin II deficiency → Megaloblastic anemia source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    false
    experimental_model
    Two infant siblings; chromatography/electrophoresis and family binding-capacity studies
    exposure
    Inherited TCII deficiency; carrier pattern supported recessive inheritance
    limitations
    Two-case family report; DNA variants were not identified and total serum B12 did not measure intracellular delivery.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Normal total B12 did not exclude a serious carrier deficiency.
    primary_references
    [hakami-1971-tcn2] Neonatal megaloblastic anemia due to inherited transcobalamin II deficiency in two siblings. (1971). https://pubmed.ncbi.nlm.nih.gov/5096637/ DOI: 10.1056/nejm197111182852103
    tissue_or_cell_type
    Systemic B12 delivery/hematopoiesis
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 530–541

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Two infant siblings; chromatography/electrophoresis and family binding-capacity studies · source_derived_draft · unverified_draft

    ### b12-abs-tcn2-inherited-functional-deficiency Two infant siblings with demonstrated transcobalamin II deficiency developed megaloblastic anemia and systemic B12-deficiency manifestations at three and five weeks despite normal total serum B12. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Normal total B12 did not exclude a serious carrier deficiency. organism: Homo sapiens tissue_or_cell_type: Systemic B12 delivery/hematopoiesis experimental_model: Two infant siblings; chromatography/electrophoresis and family binding-capacity studies limitations: Two-case family report; DNA variants were not identified and total serum B12 did not measure intracellular delivery. exposure: Inherited TCII deficiency; carrier pattern supported recessive inheritance cross_nutrient: false [hakami-1971-tcn2] Neonatal megaloblastic anemia due to inherited transcobalamin II deficiency in two siblings. (1971). https://pubmed.ncbi.nlm.nih.gov/5096637/ DOI: 10.1056/nejm197111182852103
    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.

    Evidence, AI assistance and curation standards