transcobalamins

Transcobalamins are carrier proteins which bind cobalamin (vitamin B12).

==Types== Transcobalamin I (TC-1), also known as haptocorrin (HC), R-factor, and R-protein is encoded in the human by the TCN1 gene. TC-1 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 HC-cobalamin complex. Once the complex has traveled to the more pH-neutral duodenum, pancreatic proteases degrade haptocorrin, releasing free cobalamin, which now binds to intrinsic factor (IF) for absorption by ileal enterocytes.