Vitamin B12

The prototype of a naturally occurring family of cobalt coordination compounds is called collinoids. Vitamin B12 analogues differ only in the β-ligand of cobalt, called cobalamin. Almost entirely synthesized by bacteria. Dietary sources include fish, meat, liver and dairy products; Plants have little or no cobalamin. The body converts it into biologically active forms, methylcobalamin and cobalamin, which act as enzyme cofactors. Severe deficiency may lead to megaloblastic anemia and/or neurological dysfunction.