The central core of the molecule is a tetrapyrrole with a central cobalt atom bonded to 4 pyrrole nitrogens. The action of homocysteine methyltransferase. Immature red blood cells are released into the circulation. B12 deficiency is usually seen when there is a problem in the production of intrinsic factor, which carries B12 from the gut into the blood stream. Biosynthesis of catecholamines.
Norepinephrine is the major neural transmitter of the sympathetic nervous system.
Formation of epinephrine Norepinephrine is methylated by phenylethanolamine N-methyltransferase to form epinephrine, using SAM as the methyl donor. The synthesis of melanins occurs only in pigment-producing cells called melanocytes . In these cells, melanins are synthesized from tyrosine by a sequence of several reactions. A defect in this pathway causes the disorder known as albinism . Affected individuals, who are referred to as albinos, lack pigmentation since they cannot convert tyrosine to melanins.