Vitamin B12(CAS: 68-19-9)

Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble

vitamin with a key role in the normal functioning of the brainand nervous system, and

for the formation of blood. It is one of the eight B vitamins. It is normally involved in

the metabolism of every cell of the human body, especially affecting DNA synthesis and

regulation, but also fatty acid synthesis (especially odd chain fatty acids) and energy

production. Neither fungi, plants, nor animals are capable of producing vitamin B12.

Only bacteria and archaea have the enzymes required for its synthesis, although many

foods are a natural source of B12 because of bacterial symbiosis. The vitamin is the

largest and most structurally complicated vitamin and can be produced industrially only

through bacterial fermentation-synthesis.

Vitamin B12 consists of a class of chemically related compounds (vitamers), all of which

have vitamin activity. It contains the biochemically rare element cobalt sitting in the center

of planar tetra-pyrrole ring called a Corrin ring. Biosynthesis of the basic structure of the

vitamin is accomplished only by bacteria (which usually produce hydroxocobalamin), but

conversion between different forms of the vitamin can be accomplished in the human body.

A common semi-synthetic form of the vitamin, cyanocobalamin, does not occur in nature,

but is produced from bacterial hydroxocobalamin and then used in many pharmaceuticals

and supplements, and as a food additive, because of its stability and lower production cost.

In the body it is converted to the human physiological forms methylcobalamin and

5′-deoxyadenosylcobalamin, leaving behind the cyanide, albeit in minimal concentration.

More recently, hydroxocobalamin, methylcobalamin, and adenosylcobalamin can be found in

more expensive pharmacological products and food supplements. The extra utility of these is

currently debated.

Vitamin B12 was discovered from its relationship to disease pernicious anemia, which is an

autoimmune disease in which parietal cells of the stomach responsible for secreting intrinsic

factor are destroyed, the same cells responsible for secreting acid in the stomach. Intrinsic factor

is crucial for the normal absorption of B12, so a lack of intrinsic factor, as seen in pernicious anemia,

causes a vitamin B12 deficiency. Many other subtler kinds of vitamin B12 deficiency and their

biochemical effects have since been elucidated.