in vitamin B₁₂ is replaced by hydroxide.
* methylcobalamin, the adenosyl ligand in vitamin B₁₂ is replaced by methyl.

Cyanocobalamin is a manufactured form of B₁₂. Bacterial fermentation creates AdoB₁₂ and MeB₁₂, which are converted to cyanocobalamin by the addition of potassium cyanide in the presence of sodium nitrite and heat. Once consumed, cyanocobalamin is converted