Vitamin B12 transport system

The Vitamin B12 transport system is a multi-step physiological pathway essential for the absorption and cellular delivery of cobalamin, a vital cofactor for DNA synthesis and nervous system maintenance (Green et al., 2017, Nature Reviews Disease Primers). The process begins with the binding of dietary B12 to haptocorrin, followed by its transfer to gastric intrinsic factor (IF) in the small intestine. This IF-B12 complex is then recognized by the cubam receptor complex (comprising Cubilin and Amnionless) in the terminal ileum for endocytic uptake (Nielsen et al., 2012, Nature Reviews Gastroenterology & Hepatology). Once in the bloodstream, B12 is carried by Transcobalamin II to various tissues, where it enters cells via the CD320 receptor (UniProt Consortium, 2023). Clinical targeting of this system primarily involves the administration of B12 analogues to bypass or overcome transport deficiencies, such as those seen in pernicious anemia or Imerslund-Gräsbeck syndrome (StatPearls, 2023). Additionally, the high expression of B12 receptors in certain tumors has made this system a candidate for targeted drug delivery and diagnostic imaging (PubMed, 2021).

Other names

Cobalamin transport systemIntrinsic factor-cobalamin receptor complexCbl transport systemCubam receptor complexIF-Cbl receptorTranscobalamin-mediated transport

Facilitation of cobalamin absorption via receptor-mediated endocytosis and systemic distribution through carrier proteins.