Intrinsic factor

CBLIF
Available structures
PDB	Ortholog search: PDBe RCSB
List of PDB id codes
	2PMV, 3KQ4
Identifiers
Aliases	CBLIF, IF, IFMH, INF, TCN3, gastric intrinsic factor, intrinsic factor, Intrinsic factor , IF, cobalamin binding intrinsic factor, GIF
External IDs	OMIM: 609342; MGI: 1202394; HomoloGene: 3773; GeneCards: CBLIF; OMA:CBLIF - orthologs
Gene location (Human)
Chr.	Chromosome 11 (human)
End	59,845,499 bp
Gene location (Mouse)
Chr.	Chromosome 19 (mouse)
End	11,740,811 bp
RNA expression pattern
	Top expressed in
	cardia; ; pylorus; ; body of stomach; ; testicle; ; fundus; ; buccal mucosa cell; ; gonad; ; pancreatic ductal cell; ; right lung; ; canal of the cervix;
	Top expressed in
	epithelium of stomach; ; pyloric antrum; ; mucous cell of stomach; ; left lung lobe; ; embryo; ; primary oocyte; ; quadriceps femoris muscle; ; superior colliculus; ; duodenum; ; esophagus;
	More reference expression data
	n/a
Gene ontology
Molecular function	cobalamin binding;
Cellular component	extracellular region; microvillus; endosome; lysosomal lumen; apical plasma membrane; extracellular space;
Biological process	cobalt ion transport; ion transport; cobalamin transport; cobalamin metabolic process;
	Sources:Amigo / QuickGO
Orthologs
	2694
	14603
	ENSG00000134812
	ENSMUSG00000024682
	P27352
	P52787
	NM_005142
	NM_008118
	NP_005133
	NP_032144
	Wikidata
View/Edit Human	View/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]

^ ^a ^b ^c GRCh38: Ensembl release 89: ENSG00000134812 – Ensembl, May 2017
^ ^a ^b ^c GRCm38: Ensembl release 89: ENSMUSG00000024682 – Ensembl, May 2017
^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^ ^a ^b "CBLIF - Cobalamin binding intrinsic factor precursor - Homo sapiens (Human) - CBLIF gene & protein". www.uniprot.org. Retrieved 15 March 2022.
^ Pocock G, Richards C (2006). Human Physiology: The Basis of Medicine (3rd ed.). Oxford University Press. p. 230. ISBN 978-019-856878-0.
^ ^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.
^ 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.

[refGRCh38Ensembl-1] GRCh38: Ensembl release 89: ENSG00000134812 – Ensembl, May 2017

[refGRCm38Ensembl-2] GRCm38: Ensembl release 89: ENSMUSG00000024682 – Ensembl, 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.

[uniprot-5] "CBLIF - Cobalamin binding intrinsic factor precursor - Homo sapiens (Human) - CBLIF gene & protein". www.uniprot.org. Retrieved 15 March 2022.

[Pocock_2006-6] Pocock G, Richards C (2006). Human Physiology: The Basis of Medicine (3rd ed.). Oxford University Press. p. 230. ISBN 978-019-856878-0.

[Fedosov_2012-7] 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.

[Alpers_2013-8] 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.

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