Transcobalamins are

carrier proteins A membrane transport protein (or simply transporter) is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral transmembran ...

which bind

cobalamin Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. It ...

(B₁₂).

Types

* Transcobalamin I (TCN1), also known as

haptocorrin Haptocorrin also known as transcobalamin-1 (TC-1) or cobalophilin is a transcobalamin protein that in humans is encoded by the gene. The essential function of haptocorrin is protection of the acid-sensitive vitamin B12 while it moves through the ...

, R-factor, and R-protein, is a glycoprotein produced by the

salivary glands The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gla ...

of the mouth. It primarily serves to protect

(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 Intrinsic factor (IF), cobalamin binding intrinsic factor, 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 o ...

for absorption by ileal enterocytes. * Transcobalamin II (TCN2) binds cobalamin once it has been taken up by

enterocytes Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells which line the inner surface of the small and large intestines. A glycocalyx surface coat contains digestive enzymes. Microvilli on the apical surface increase its s ...

of the terminal ileum and the "Intrinsic Factor-Vitamin B12" complex has been degraded. Transcobalamin II is then involved with the transport of Vitamin B12 to the tissues.

References

External links

* {{Globulins