Hydroxocobalamin (OHCbl)

Hydroxocobalamin is a naturally occurring form of Vitamin B12 and a member of the cobalamin family of compounds. It serves as a vital precursor to the active coenzymes methylcobalamin and adenosylcobalamin, which are essential for DNA synthesis, fatty acid metabolism, and the maintenance of the myelin sheath in the nervous system (PubChem CID 5460482; StatPearls: Vitamin B12 Deficiency). Specifically, it acts as a cofactor for methionine synthase and methylmalonyl-CoA mutase, playing a key role in converting homocysteine to methionine and methylmalonyl-CoA to succinyl-CoA (NIH Office of Dietary Supplements). In clinical practice, hydroxocobalamin is widely recognized as a first-line antidote for acute cyanide poisoning due to its high affinity for cyanide ions, which it binds to form the non-toxic cyanocobalamin for renal excretion (FDA: Cyanokit). It is also used to treat various B12 deficiency states, including pernicious anemia and dietary insufficiency. While it is a critical pharmacological agent, hydroxocobalamin is classified as a vitamin or cofactor rather than a traditional therapeutic target like a receptor or enzyme (UniProt).

Other names

Vitamin B12aHydroxycobalaminVitamin B12bHydroxocobalaminum

Hydroxocobalamin acts as a cofactor for methionine synthase and methylmalonyl-CoA mutase; it also functions as a cyanide scavenger by chelating cyanide ions to form cyanocobalamin.