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see coenzymecoenzyme
, any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes. A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in
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; vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(or Vitamin B12), C63H88CoN14O14P, a cobalt-corrin complex in which the cobalt atom is bonded to a cyano group, a nucleotide residue, and four reduced pyrrole rings; molecular weight, 1355.40. Cyanocobalamin is a dark-red crystalline compound, which is soluble in water and polar organic solvents. It was first isolated in crystalline form from cattle liver. Its structure was established by A. Todd and D. Crowfoot Hodgkin and their co-workers.

The primary sources of cyanocobalamin in nature are microorganisms; cyanocobalamin is synthesized by several bacteria, by actinomycetes, and by blue-green algae. It occurs in almost all animal tissues. It is not encountered, as a rule, in the tissues of higher plants (legume tubers are an exception). In ruminants, it is synthesized in sufficient amounts by the microflora of the intestine and the rumen. In man and several higher animals, such as birds and hogs, its synthesis by intestinal microflora is insufficient, and thus the vitamin must be obtained from food. The daily requirement for humans is about 5 μg. The major sources of the vitamin are liver, kidneys, fish meal, and milk.

In the form of its coenzymes methylcobalamin and deoxyadenosylcobalamin, cyanocobalamin participates in the enzymic reactions involved in hematopoiesis and facilitates normal liver function and nerve fiber regeneration. It is produced by microbiological synthesis using propionic-acid bacteria for the fermentation process.

Vitamin B12 is used for the treatment of pernicious anemia and other anemias, as well as of diseases of the central and peripheral nervous systems and the liver. It is prescribed in solutions for intramuscular injections. (See alsoVITAMINS; ANEMIA; and COBALAMINS.)


Smith, L. Vitamin B12. Moscow, 1962. (Translated from English.)
Friedrich, W. Vitamin B12 und Verwandte Corrinoide, 3rd ed. Stuttgart, 1975.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


vitamin B12
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
[5] Nonstandard abbreviations: MMA, methylmalonic acid; ALT, alanine transaminase; AST, aspartate transaminase; RDW, red cell distribution width; HCT, hematocrit; EMG, electromyography; Cbl, cobalamin; Met, methionine; Hcy, homocysteine; AdoCbl, adenosylcobalamin; MeCbl, methylcobalamin; tHcy, total Hcy; 2MCA, 2-methylcitric acid; SCD, subacute combined degeneration of spinal cord; PA, pernicious anemia; [N.sub.2]O, nitrous oxide; GDS, Global Drug Survey; SAM, 5- adenosykmethionine; Hb, hemoglobin.
Cells were spiked with 150ng/ml phorbol-12-myristate 13-acetate and methylcobalamin (0,200,500,750, and 1000 pg/ml) or hydroxocobalamin (0,200,500,750, and 1000 pg/ml) and incubated for 24 hours at 37[degrees]C, 5% C[O.sub.2].
Efficacy and tolerability of a fixed dose combination of Methylcobalamin and Pregabalin in the management of painful neuropathy.
Fuchs et al., "Efficacy of methylcobalamin and folinic acid treatment on glutathione redox status in children with autism," American Journal of Clinical Nutrition, vol.
A randomized multicenter trial (N=214) found that adding a supplement containing L-methylfolate 3 mg, pyridoxal 5-phosphate 35 mg, and methylcobalamin 2 mg twice daily to other medications (eg, pregabalin, gabapentin, or duloxetine) improved symptoms of diabetic neuropathy.
In these cases, supplementation with 5-methylfolate, pyridoxal-5-phosphate, methylcobalamin, and betaine can be corrective (18,19).
An ultra-high dose of methylcobalamin (methyl-B12), may up-regulate gene transcription and thereby protein synthesis, and be of clinical use for patients with peripheral neuropathies, and clients may wish to discuss with their medical practitioner (Watanabe, Kaji, Oka, Bara, & Kimura, 1994; Life Extension, 1998).
Early co-administration of vitamin E and methylcobalamin after induction of sciatic nerve crush lesion ameliorated neuropathic pain responses by improving paw withdrawal latency and motor nerve conduction velocity in rats (Morani and Bodhankar, 2010).
SAMe is also needed for methylation of DNA, myelin, production of methylcobalamin, creatine, phosphatidylcholine, melatonin, coenzyme Q10, and epinephrine.
Vitamin B12 has some analogs including cyanocobalamin (CNCbl), methylcobalamin (MeCbl), hydroxocobalamin (OHCbl), and adenosylcobalamin (AdoCbl).
(15) It contains high concentrations of the bioavailable forms of folate (L-methylfolate calcium) 3 mg, vitamin B12 (methylcobalamin) 2 mg, and vitamin B6 (pyridoxal-5'phosphate) 35 mg (LMF-MC-PLP [Metanx; Nestle Health Science-Pamlab, Inc, Covington, LA]).
Thus, to neutralize toxicity in the food we could possibly ingest, consider a supplement called vitamin B12 (methylcobalamin).