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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 Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved.
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 It might be outdated or ideologically biased.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.
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One serving of walleye also supplies 22 percent of the DRI of thiamin, 13 percent of riboflavin, 15 percent of niacin, 15 percent of pantothenic acid and 82 percent of B-12.
Although it is only required in micro amounts, vitamin B-12 is vital to the formation of healthy red blood cells and it helps build everything from genetic material (DNA) to hormones and other proteins.
Participants with a higher intake of niacin, folate, B-6 or B-12 were older, more likely to be female and white, exercised more, and had a higher education level.
She said the results don't tell them whether the high folate levels or high vitamin B-12 caused the autism risk, or whether certain genes led to the high folate levels and increased autism risk through some other mechanism.
A: With age, the body loses some of its ability to absorb vitamin B-12 from food.
The management strategy of the adult patient in our report was planned by considering existing B-12 deficiency and the operation performed subsequently, a total gastrectomy.
An estimated 15 percent of people over 65 have a vitamin B-12 deficiency, possibly because of impaired absorption related to medications, poor dietary practices, or health conditions such as intestinal disorders.
B-12 for injection is also available by prescription.
MinuteClinic, a provider of retail-based medical clinics in the US, said on Monday that it has expanded its suite of accessible and affordable health care services to include Vitamin B-12 injections and the Human Papillomavirus (HPV) vaccination (GARDASIL).
We changed a vitamin B-12 molecule by removing a portion of it and replacing it with nitric oxide, a compound made of the elements nitrogen and oxygen.
Focusing on specific nutrients, a study conducted at Brigham and Women's Hospital and Harvard Medical School and published recently in the Archives of Internal Medicine found that taking a combination of vitamins B-6 and B-12 and folic acid decreases the risk of AMD in women.
Certain psychotic conditions (delusions, hallucinations) and mental disturbances can be helped with vitamins B-6, B-9, B-12, and zinc.