Component

Human haptocorrin / TCN1

Human haptocorrin / TCN1

7 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. In egg-yolk transfer assays, human R binder accepted released cobalamin, whereas direct transfer to intrinsic factor was not detected and R-binder-deficient gastric juice failed to accept it.

    Human haptocorrin / TCN1 → Vitamin B12 (cobalamins) source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice
    exposure
    Acidified human saliva/gastric juice with egg-yolk-bound radiocobalamin
    limitations
    Food-specific biochemical model; this pH threshold is not a clinical blood threshold or proof that all foods behave identically. Pepsin preparation species was not specified in the inspected abstract.
    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 first observed carrier was haptocorrin.
    primary_references
    [carmel-1990-food-transfer] Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice. (1990). https://pubmed.ncbi.nlm.nih.gov/2110915/ DOI: 10.1016/0016-5085(90)91076-i
    tissue_or_cell_type
    Gastric luminal digestion model

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 114–125

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice · source_derived_draft · unverified_draft

    ### b12-abs-food-haptocorrin-capture In egg-yolk transfer assays, human R binder accepted released cobalamin, whereas direct transfer to intrinsic factor was not detected and R-binder-deficient gastric juice failed to accept it. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: The first observed carrier was haptocorrin. organism: Homo sapiens tissue_or_cell_type: Gastric luminal digestion model experimental_model: In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice limitations: Food-specific biochemical model; this pH threshold is not a clinical blood threshold or proof that all foods behave identically. Pepsin preparation species was not specified in the inspected abstract. exposure: Acidified human saliva/gastric juice with egg-yolk-bound radiocobalamin cross_nutrient: false [carmel-1990-food-transfer] Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice. (1990). https://pubmed.ncbi.nlm.nih.gov/2110915/ DOI: 10.1016/0016-5085(90)91076-i
    Complete structured claim and evidence

  2. Human salivary R protein bound cobalamin with 50-fold higher affinity than human intrinsic factor at pH 2 and threefold higher affinity at pH 8.

    Human haptocorrin / TCN1 → Vitamin B12 (cobalamins) source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    Purified human salivary R protein and gastric intrinsic factor in vitro
    exposure
    pH 2 or 8; purified protein competition
    limitations
    Reconstituted binding/protease conditions; measured competition does not quantify absorption in an intact person. Individual protease isoforms and reagent species not resolved in abstract.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Haptocorrin outcompeted intrinsic factor, especially in acid.
    primary_references
    [allen-1978-proteases] Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/22556/ DOI: 10.1172/jci108924
    tissue_or_cell_type
    Salivary/gastric and intestinal luminal binding models

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 153–164

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human salivary R protein and gastric intrinsic factor in vitro · source_derived_draft · unverified_draft

    ### b12-abs-haptocorrin-affinity Human salivary R protein bound cobalamin with 50-fold higher affinity than human intrinsic factor at pH 2 and threefold higher affinity at pH 8. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Haptocorrin outcompeted intrinsic factor, especially in acid. organism: Homo sapiens tissue_or_cell_type: Salivary/gastric and intestinal luminal binding models experimental_model: Purified human salivary R protein and gastric intrinsic factor in vitro limitations: Reconstituted binding/protease conditions; measured competition does not quantify absorption in an intact person. Individual protease isoforms and reagent species not resolved in abstract. exposure: pH 2 or 8; purified protein competition cross_nutrient: false [allen-1978-proteases] Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/22556/ DOI: 10.1172/jci108924
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. In the egg-yolk/human saliva model, acidification to pH 1.5 permitted limited cobalamin transfer to R binder; virtually none occurred above pH 2 despite pepsin.

    Hydrogen ion → Egg-yolk cobalamin transfer to human haptocorrin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice
    exposure
    In vitro pH manipulation
    limitations
    Food-specific biochemical model; this pH threshold is not a clinical blood threshold or proof that all foods behave identically. Pepsin preparation species was not specified in the inspected abstract.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Acid enabled release and capture of B12 from this food model.
    primary_references
    [carmel-1990-food-transfer] Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice. (1990). https://pubmed.ncbi.nlm.nih.gov/2110915/ DOI: 10.1016/0016-5085(90)91076-i
    tissue_or_cell_type
    Gastric luminal digestion model

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 88–99

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice · source_derived_draft · unverified_draft

    ### b12-abs-food-acid In the egg-yolk/human saliva model, acidification to pH 1.5 permitted limited cobalamin transfer to R binder; virtually none occurred above pH 2 despite pepsin. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Acid enabled release and capture of B12 from this food model. organism: Homo sapiens tissue_or_cell_type: Gastric luminal digestion model experimental_model: In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice limitations: Food-specific biochemical model; this pH threshold is not a clinical blood threshold or proof that all foods behave identically. Pepsin preparation species was not specified in the inspected abstract. exposure: In vitro pH manipulation cross_nutrient: false [carmel-1990-food-transfer] Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice. (1990). https://pubmed.ncbi.nlm.nih.gov/2110915/ DOI: 10.1016/0016-5085(90)91076-i
    Complete structured claim and evidence

  2. Adding pepsin at 1,200 U/mL under acidic conditions increased egg-yolk cobalamin transfer to human salivary or gastric R binders to 39-58%.

    Pepsin A enzyme family → Egg-yolk cobalamin transfer to human haptocorrin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice
    exposure
    Pepsin supplementation at acidic pH
    limitations
    Food-specific biochemical model; this pH threshold is not a clinical blood threshold or proof that all foods behave identically. Pepsin preparation species was not specified in the inspected abstract.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Pepsin helped haptocorrin capture food-bound B12.
    primary_references
    [carmel-1990-food-transfer] Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice. (1990). https://pubmed.ncbi.nlm.nih.gov/2110915/ DOI: 10.1016/0016-5085(90)91076-i
    tissue_or_cell_type
    Gastric luminal digestion model

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 101–112

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice · source_derived_draft · unverified_draft

    ### b12-abs-food-pepsin Adding pepsin at 1,200 U/mL under acidic conditions increased egg-yolk cobalamin transfer to human salivary or gastric R binders to 39-58%. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Pepsin helped haptocorrin capture food-bound B12. organism: Homo sapiens tissue_or_cell_type: Gastric luminal digestion model experimental_model: In vitro egg-yolk cobalamin-binding protein mixed with human saliva/gastric juice limitations: Food-specific biochemical model; this pH threshold is not a clinical blood threshold or proof that all foods behave identically. Pepsin preparation species was not specified in the inspected abstract. exposure: Pepsin supplementation at acidic pH cross_nutrient: false [carmel-1990-food-transfer] Transfer of cobalamin from the cobalamin-binding protein of egg yolk to R binder of human saliva and gastric juice. (1990). https://pubmed.ncbi.nlm.nih.gov/2110915/ DOI: 10.1016/0016-5085(90)91076-i
    Complete structured claim and evidence

  3. In three patients with pancreatic insufficiency, oral cobinamide 100 nmol corrected malabsorption of 0.4 nmol radiocobalamin in Schilling tests, comparably to trypsin.

    Cobinamide → Intestinal cobalamin absorption source_derived_draftungraded
    Experimental context and source evidence
    availability_state
    machinery_impairment Imported condition classification; unverified.
    cross_nutrient
    false
    experimental_model
    Three human pancreatic-insufficiency patients and parallel human binding assays
    exposure
    Cobinamide competitor during Schilling test
    limitations
    Small physiological intervention; cobinamide is an experimental analogue, not B12 nutrition. The absorption defect was pancreatic machinery impairment.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Blocking haptocorrin competition restored tracer absorption in three patients.
    primary_references
    [allen-1978-cobinamide] Correction of cobalamin malabsorption in pancreatic insufficiency with a cobalamin analogue that binds with high affinity to R protein but not to intrinsic factor. In vivo evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/659618/ DOI: 10.1172/jci109083
    tissue_or_cell_type
    Intestinal absorption and urinary radiotracer recovery
    trigger_kind
    machinery_impairment Imported condition classification; unverified.

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 205–216

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Three human pancreatic-insufficiency patients and parallel human binding assays · source_derived_draft · unverified_draft

    ### b12-abs-pancreatic-competitor-rescue In three patients with pancreatic insufficiency, oral cobinamide 100 nmol corrected malabsorption of 0.4 nmol radiocobalamin in Schilling tests, comparably to trypsin. Condition category: machinery_impairment nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Blocking haptocorrin competition restored tracer absorption in three patients. organism: Homo sapiens tissue_or_cell_type: Intestinal absorption and urinary radiotracer recovery experimental_model: Three human pancreatic-insufficiency patients and parallel human binding assays limitations: Small physiological intervention; cobinamide is an experimental analogue, not B12 nutrition. The absorption defect was pancreatic machinery impairment. exposure: Cobinamide competitor during Schilling test cross_nutrient: false [allen-1978-cobinamide] Correction of cobalamin malabsorption in pancreatic insufficiency with a cobalamin analogue that binds with high affinity to R protein but not to intrinsic factor. In vivo evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/659618/ DOI: 10.1172/jci109083
    Complete structured claim and evidence

  4. Pancreatic protease incubation at pH 8 partially degraded human R protein and lowered its cobalamin affinity approximately 150-fold.

    Pancreatic serine protease family → Human haptocorrin affinity for cobalamin source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    Purified human salivary R protein and gastric intrinsic factor in vitro
    exposure
    Pancreatic proteases at pH 8
    limitations
    Reconstituted binding/protease conditions; measured competition does not quantify absorption in an intact person. Individual protease isoforms and reagent species not resolved in abstract.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Digestive proteases loosened haptocorrin binding.
    primary_references
    [allen-1978-proteases] Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/22556/ DOI: 10.1172/jci108924
    tissue_or_cell_type
    Duodenal luminal model

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 166–177

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human salivary R protein and gastric intrinsic factor in vitro · source_derived_draft · unverified_draft

    ### b12-abs-proteolysis-affinity Pancreatic protease incubation at pH 8 partially degraded human R protein and lowered its cobalamin affinity approximately 150-fold. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Digestive proteases loosened haptocorrin binding. organism: Homo sapiens tissue_or_cell_type: Duodenal luminal model experimental_model: Purified human salivary R protein and gastric intrinsic factor in vitro limitations: Reconstituted binding/protease conditions; measured competition does not quantify absorption in an intact person. Individual protease isoforms and reagent species not resolved in abstract. exposure: Pancreatic proteases at pH 8 cross_nutrient: false [allen-1978-proteases] Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/22556/ DOI: 10.1172/jci108924
    Complete structured claim and evidence

  5. Protease treatment of R-protein-bound cobalamin enabled complete transfer to human intrinsic factor within ten minutes; without proteases, transfer was not observed at pH 2 or 8.

    Pancreatic serine protease family → Cobalamin transfer from haptocorrin to human intrinsic factor source_derived_draftungraded
    Experimental context and source evidence
    cross_nutrient
    false
    experimental_model
    Purified human salivary R protein and gastric intrinsic factor in vitro
    exposure
    R protein-Cbl plus pancreatic proteases and IF
    limitations
    Reconstituted binding/protease conditions; measured competition does not quantify absorption in an intact person. Individual protease isoforms and reagent species not resolved in abstract.
    nutrient_topic
    Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. · Vitamin B12 (cobalamins)
    organism
    Homo sapiens
    plain_language
    Proteolysis enabled B12 to switch carriers.
    primary_references
    [allen-1978-proteases] Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/22556/ DOI: 10.1172/jci108924
    tissue_or_cell_type
    Duodenal luminal model

    Vitamin B12: mechanisms, deficiency and nutrient interactions (2026-09-17) · lines 179–190

    AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Purified human salivary R protein and gastric intrinsic factor in vitro · source_derived_draft · unverified_draft

    ### b12-abs-proteolysis-transfer Protease treatment of R-protein-bound cobalamin enabled complete transfer to human intrinsic factor within ten minutes; without proteases, transfer was not observed at pH 2 or 8. Condition category: normal nutrient_topic: Vitamin B12 research collection; topical membership is not evidence of a direct dietary effect. plain_language: Proteolysis enabled B12 to switch carriers. organism: Homo sapiens tissue_or_cell_type: Duodenal luminal model experimental_model: Purified human salivary R protein and gastric intrinsic factor in vitro limitations: Reconstituted binding/protease conditions; measured competition does not quantify absorption in an intact person. Individual protease isoforms and reagent species not resolved in abstract. exposure: R protein-Cbl plus pancreatic proteases and IF cross_nutrient: false [allen-1978-proteases] Effect of proteolytic enzymes on the binding of cobalamin to R protein and intrinsic factor. In vitro evidence that a failure to partially degrade R protein is responsible for cobalamin malabsorption in pancreatic insufficiency. (1978). https://pubmed.ncbi.nlm.nih.gov/22556/ DOI: 10.1172/jci108924
    Complete structured claim and evidence

In the sources

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

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