Effects of Exogenous L-Dopa on the Metabolism of Methionine and S-Adenosylmethionine in the Brain
The catecholamines dopamine, norepinephrine, and epinephrine are metabolized by oxidative deamination and by O-methylation. This latter pathway is catalyzed by the enzyme catechol-O-methyl-transferase (1); it utilizes S-adenosyl-methionine (SAMe) as the methyl donor (Fig. 1), and its products are, for the most part, methylated on the metahydroxyl group. The catecholamines themselves are formed within only a few specific tissues in the body (21). These include a relatively small number of brain neurons, postganglionic sympathetic neurons, adrenomedullary chromaffin cells, and interneurons within sympathetic ganglia. The catechol-amines can be O-methylated within their cells of origin, within synapses, or, after secretion into the blood stream, within the liver, kidneys, and other organs.
KeywordsDopamine Folate Norepinephrine Epinephrine Catecholamine
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