Human Metabolome Database: Cyanocobalamin
Description
B12 is the most chemically complex of all the vitamins. B12's structure is based on a corrin ring, which, although similar to the porphyrin ring found in heme, chlorophyll, and cytochrome, has two of the pyrrole rings directly bonded. The central metal ion is Co (cobalt). B12 cannot be made by plants or by animals[3], as the only type of organisms that have the enzymes required for the synthesis of B12 are bacteria and archaea. Higher plants do not concentrate vitamin B 12 from the soil and so are a poor source of the substance as compared with animal tissues. Vitamin B12 is naturally found in foods including meat (especially liver and shellfish), eggs, and milk products.
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