Cubilin-amnionless receptor (null)

Vitamin B12 absorption is a multi-step process requiring the release of B12 from dietary proteins in the stomach, its complexation with haptocorrin (R-protein), transfer to intrinsic factor in the duodenum, and subsequent absorption in the distal ileum via binding of the B12–intrinsic factor complex to the cubilin-amnionless membrane receptor complex (cubam receptor) on enterocytes. Inherited or acquired defects in any component of this pathway can lead to B12 deficiency, affecting hematologic and neurologic health. While multiple proteins are involved, the most specific and druggable "target" for absorption in humans is the cubilin-amnionless receptor.

Other names

Cubam receptorCubilin–amnionless complexIF–cobalamin receptorCUBN-AMN complexIntrinsic factor–vitamin B12 receptor

For drugs affecting absorption (indirect): Inhibition of acid production (proton pump inhibitors) reduces B12 release from food. For supplement therapy: Providing vitamin B12 in very high doses permits passive diffusion, bypassing the receptor-mediated pathway.