Cyanocobalamin metabolic enzymes and transport proteins

The cyanocobalamin metabolic enzymes and transport proteins constitute a complex multi-protein network responsible for the absorption, systemic transport, and intracellular conversion of vitamin B12 into its active coenzyme forms. This system includes gastric intrinsic factor (GIF) and haptocorrin for gastrointestinal transport, the cubam receptor complex for ileal uptake, and transcobalamin II (TCN2) for delivery to peripheral tissues via the CD320 receptor. Intracellularly, proteins such as MMACHC and MMADHC process the vitamin, which then serves as a vital cofactor for methionine synthase (MTR) in the cytosol and methylmalonyl-CoA mutase (MUT) in the mitochondria. Dysfunctions in this pathway, whether due to genetic mutations or acquired factors like autoimmune destruction of parietal cells (pernicious anemia), lead to severe hematological and neurological disorders, including megaloblastic anemia and subacute combined degeneration of the spinal cord. Therapeutic intervention primarily involves supplementation with various cobalamin forms, while certain drugs like metformin and proton pump inhibitors are known to interfere with this pathway, necessitating clinical monitoring.

Other names

Vitamin B12 transport and metabolism systemCobalamin metabolic pathwayB12 trafficking networkCyanocobalamin metabolic pathway