Transcobalamin

transcobalamin I (vitamin B12 binding protein, R binder family)
Identifiers
Symbol	TCN1
Entrez	6947
HUGO	11652
OMIM	189905
RefSeq	NM_001062
UniProt	P20061
Other data
Locus	Chr. 11 q11-q12

transcobalamin II; macrocytic anemia
Identifiers
Symbol	TCN2
Entrez	6948
HUGO	11653
OMIM	275350
RefSeq	NM_000355
UniProt	P20062
Other data
Locus	Chr. 22 q11.2-qter

Transcobalamins are carrier proteins which bind cobalamin (B₁₂).

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 uptaken by enterocytes of the terminal ileum and the "Intrinsic Factor-Vitamin B12" complex has been degraded. The TCII-Vit B12 complex then enters portal circulation and is processed in the liver.

External links

• Transcobalamins at the US National Library of Medicine Medical Subject Headings (MeSH)