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Abstract
Cobalamins, (Cbls, vitamin B12 derivatives), are octahedrally coordinated cobalt(III) macrocycles incorporating a range of ligands at the upper (= ) axial site. These include aqua/hydroxy (H2OCbl+/HOCbl; pKa(H2OCbl+) = 7.76, cyanide (CNCbl), methyl (MeCbl), 5’-deoxyadenosyl (AdoCbl), nitro (NO2Cbl) and nitrosyl (NOCbl) ligands.
Vitamin B12 (Cobalamins) is involved in the metabolism of every cell in the body. There are two enzymatic reactions involving vitamin B12 as a co-enzyme in humans. The first, methionine synthase. The second mammalian B12-dependent enzyme reaction, L-methylmalonyl-coenzyme A mutase. Vitamin B12 deficiency in humans leads to hyperhomocysteinemia and/or methylmalonic acidemia followed by megaloblastic anemia and neurological disorders.
The nitric oxide (NO) derivative of vitamin B12, nitroxylcobalmin (NOCbl, also referred to as nitrosylcobalmin or nitrosocobalamin in the literature), is of potential interest in mammalian biochemistry. It has been suggested that cobalamins scavenge nitric oxide to form NOCbl in vivo. Cobalamin may be beneficial in treating pathological disorders associated with high NO, including sepsis.