B12 chemistry, its two human cofactor systems, and the need to identify the exact cobalamin form.
Vitamin B12 refers to a family of cobalt-containing cobalamins rather than one peptide or one molecular form. Cyanocobalamin, hydroxocobalamin, methylcobalamin, and adenosylcobalamin differ chemically and should not be treated as interchangeable reference standards.
What researchers examine
Humans have two established B12-dependent enzymes: cytosolic methionine synthase and mitochondrial methylmalonyl-CoA mutase. Their cofactor chemistry connects one-carbon metabolism, methionine production, and conversion of methylmalonyl-CoA to succinyl-CoA.
Identity matters
The catalog strength describes material mass, not a use amount. Before any study, the certificate of analysis should identify the cobalamin form, counterions, water content, purity method, and light-sensitivity controls. A generic B12 label is insufficient for mechanistic equivalence.
Primary source
Research-use notice: For laboratory research use only. Not for human or veterinary use, ingestion, injection, therapeutic, diagnostic, or clinical use. This educational material summarizes research context; it is not medical advice and does not establish safety, efficacy, identity, purity, or suitability for any use.