Intrinsic factor

GIF
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 2PMV, 3KQ4
Identifiers
Aliases	GIF, IF, IFMH, INF, TCN3, gastric intrinsic factor, Intrinsic factor , IF
External IDs	OMIM: 609342 MGI: 1202394 HomoloGene: 3773 GeneCards: GIF
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 • transport • cobalamin transport • cobalamin metabolic process Sources:Amigo / QuickGO
Orthologs
Species	Human	Mouse
Entrez	2694	14603
Ensembl	ENSG00000134812	ENSMUSG00000024682
UniProt	P27352	P52787
RefSeq (mRNA)	NM_005142	NM_008118
RefSeq (protein)	NP_005133	NP_032144.2 NP_032144
Location (UCSC)	Chr 11: 59.83 – 59.85 Mb	Chr 19: 11.75 – 11.76 Mb
PubMed search

2PMV, 3KQ4

2694

14603

ENSG00000134812

ENSMUSG00000024682

P27352

P52787

NM_005142

NM_008118

NP_005133

NP_032144.2
NP_032144

Intrinsic factor (IF), also known as gastric intrinsic factor (GIF), is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B₁₂ (cobalamin) later on in the small intestine. In humans, the gastric intrinsic factor protein is encoded by the GIF gene.

(also known as HC, R protein, and transcobalamin I, TCN1) is a glycoprotein secreted by the salivary glands which binds to vitamin B₁₂. Vitamin B₁₂ is acid sensitive and in binding to transcobalamin I it can safely pass through the acidic stomach to the duodenum. In the less acidic environment of the small intestine, pancreatic enzymes digest the glycoprotein carrier and vitamin B₁₂ can then bind to intrinsic factor. This new complex is then absorbed by the epithelial cells (enterocytes) of the ileum. Inside the cells, B₁₂ dissociates once again and binds to another protein, transcobalamin II (TCN2); the new complex can then exit the epithelial cells to be carried to the liver.

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Wikipedia