Transcobalamin

Transcobalamins are carrier proteins which bind cobalamin (B12).

transcobalamin I (vitamin B12 binding protein, R binder family)
Identifiers
SymbolTCN1
NCBI gene6947
HGNC11652
OMIM189905
RefSeqNM_001062
UniProtP20061
Other data
LocusChr. 11 q11-q12
transcobalamin II; macrocytic anemia
Identifiers
SymbolTCN2
NCBI gene6948
HGNC11653
OMIM275350
PDB2BB5
RefSeqNM_000355
UniProtP20062
Other data
LocusChr. 22 q11.2-qter

Types
  • Transcobalamin I (TCN1), also known as haptocorrin, R-factor, and R-protein, is a glycoprotein produced by the salivary glands of the mouth. It primarily serves to protect cobalamin (Vitamin B12) from acid degradation in the stomach by producing a Haptocorrin-Vitamin B12 complex. Once the complex has traveled to the more neutral duodenum, pancreatic proteases degrade haptocorrin, releasing free cobalamin, which now binds to intrinsic factor for absorption by ileal enterocytes.
  • Transcobalamin II (TCN2) binds cobalamin once it has been taken up by enterocytes of the terminal ileum and the "Intrinsic Factor-Vitamin B12" complex has been degraded. Trancobalamin II is then involved with the transport of Vitamin B12 to the tissues.[1]

References
  1. Rachmilewitz B, Rachmilewitz M, Chaouat M, Schlesinger M (July 1977). "The synthesis of transcobalamin II, a vitamin B12 transport protein, by stimulated mouse peritoneal macrophages". Biomédicine. 27 (6): 213–4. PMID 907799.


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