is used to make SAMe. SAMe is the universal methyl donor and is used for DNA methylation and to make phospholipid membranes, choline, sphingomyelin, acetylcholine, and other neurotransmitters. In mitochondria The enzymes that use as a built-in cofactor are methylmalonyl-CoA mutase (PDB 4REQ) and methionine synthase (PDB 1Q8J). The metabolism of propionyl-CoA occurs in the mitochondria and requires Vitamin (as adenosylcobalamin) to make succinyl-CoA. When the conversion of propionyl-CoA to succinyl-CoA in the mitochondria fails due to Vitamin deficiency, elevated blood levels of methylmalonic acid (MMA) occur. Thus, elevated blood levels of homocysteine and MMA may both be indicators of vitamin deficiency. Adenosylcobalamin is needed as cofactor in methylmalonyl-CoA mutase—MUT enzyme. Processing of cholesterol and protein gives propionyl-CoA that is converted to methylmalonyl-CoA, which is used by MUT enzyme to make succinyl-CoA. Vitamin is needed to prevent anemia, since making porphyrin and heme in mitochondria for producing hemoglobin in red blood cells depends on succinyl-CoA made by vitamin . Absorption and transport Inadequate absorption of vitamin may be related to coeliac disease. Intestinal absorption of vitamin requires successively three different protein molecules: haptocorrin, intrinsic factor and transcobalamin II. See also Methylcobalamin Hydroxocobalamin Adenosylcobalamin Cobalamin biosynthesis References External links B vitamins Organocobalt compounds Cofactors Vitamin B12 Corrinoids Wikipedia medicine articles ready to translate pt:Cianocobalamina