Intrinsic factor

CBLIF
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesCBLIF, IF, IFMH, INF, TCN3, gastric intrinsic factor, intrinsic factor, Intrinsic factor , IF, cobalamin binding intrinsic factor, GIF
External IDsOMIM: 609342; MGI: 1202394; HomoloGene: 3773; GeneCards: CBLIF; OMA:CBLIF - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_005142

NM_008118

RefSeq (protein)

NP_005133

NP_032144

Location (UCSC)Chr 11: 59.83 – 59.85 MbChr 19: 11.72 – 11.74 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Intrinsic factor (IF), cobalamin binding intrinsic factor,[5] also known as gastric intrinsic factor (GIF), is a glycoprotein produced by the parietal cells (in humans) or chief cells (in rodents) of the stomach. It is necessary for the absorption of vitamin B12 later on in the distal ileum of the small intestine.[6] In humans, the gastric intrinsic factor protein is encoded by the CBLIF gene.[5] Haptocorrin (transcobalamin I) is another glycoprotein secreted by the salivary glands which binds to vitamin B12. Vitamin B12 is acid-sensitive and in binding to haptocorrin it can safely pass through the acidic stomach to the duodenum.[7]

In the less acidic environment of the small intestine, pancreatic enzymes digest the glycoprotein carrier and vitamin B12 can then bind to intrinsic factor.[7] This new complex is then absorbed by the epithelial cells (enterocytes) of the ileum.[7] Inside the cells, vitamin B12 dissociates once again and binds to another protein, transcobalamin II; the new complex can then exit the epithelial cells to be carried to the liver.[8]

  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000134812Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000024682Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ a b "CBLIF - Cobalamin binding intrinsic factor precursor - Homo sapiens (Human) - CBLIF gene & protein". www.uniprot.org. Retrieved 15 March 2022.
  6. ^ Pocock G, Richards C (2006). Human Physiology: The Basis of Medicine (3rd ed.). Oxford University Press. p. 230. ISBN 978-019-856878-0.
  7. ^ a b c Fedosov SN (2012). "Physiological and Molecular Aspects of Cobalamin Transport". Water Soluble Vitamins. (review). Subcellular Biochemistry. Vol. 56. pp. 347–67. doi:10.1007/978-94-007-2199-9_18. ISBN 978-94-007-2198-2. PMID 22116708.
  8. ^ Alpers DH, Russell-Jones G (May 2013). "Gastric intrinsic factor: the gastric and small intestinal stages of cobalamin absorption. A personal journey". (review). Biochimie. 95 (5): 989–94. doi:10.1016/j.biochi.2012.12.006. PMID 23274574.