Haptocorrin (HC)

Haptocorrin, also known as Transcobalamin-1 or R-binder, is a heavily glycosylated protein encoded by the TCN1 gene that plays a critical role in the transport and protection of Vitamin B12 (cobalamin). Produced primarily by salivary glands and found in various secretions and plasma, it binds Vitamin B12 with high affinity to protect it from degradation by gastric acid in the stomach. In the duodenum, haptocorrin is degraded by pancreatic proteases, allowing the released Vitamin B12 to bind to Intrinsic Factor for intestinal absorption. Beyond its physiological role in B12 metabolism, haptocorrin serves as a diagnostic biomarker for myeloproliferative disorders and certain cancers, such as fibrolamellar hepatocellular carcinoma, where its levels are significantly elevated. Recent therapeutic strategies explore haptocorrin as a vehicle for drug delivery, utilizing its binding capacity to improve the pharmacokinetics and half-life of conjugated peptide drugs.

Other names

Transcobalamin-1Transcobalamin ITCN1R-binderR-proteinCobalophilinSalivary R-factor

Haptocorrin binds dietary Vitamin B12 in the oral cavity and stomach with high affinity, forming a complex that is resistant to low pH, thereby protecting the vitamin from acid-induced denaturation. In the duodenum, the protein is degraded by pancreatic proteases, releasing the vitamin for subsequent binding to Intrinsic Factor.