3 ,4 -Dihydroxyphenylethylamine

L-Dihydroxyphenylalanine 4-Dihydroxyphenylethylamine Dimeric Transcription Factors Dioxins Dipeptidase Dipeptidylpeptidase Dipeptidylpeptidase IV Direct Thrombin Inhibitors Discharge of Neurons... 

Dopamine (3 4 dihydroxyphenylethylamine), like noradrenaline and adrenaline, is a eateeholamine and in addition to its independent neurotransmitter role in the CNS it is a preeursor to noradrenaline (NA) in all central and peripheral noradrenegic neurons. 

This enzyme rapidly deaminates certain primary and secondary unsubstituted p-hy-droxy- and 3,4-dihydroxyphenylethylamines wherein the amino group is on the terminal carbon atom of the side chain (4,18, 22,40,128). 

Histamine, serotonin and the catecholamines (dopamine, epinephrine and norepinephrine) are synthesized from the aromatic amino acids histidine, tryptophan and phenylalanine, respectively. The biosynthesis of catecholamines in adrenal medulla cells and catecholamine-secreting neurons can be simply summarized as follows [the enzyme catalysing the reaction and the key additional reagents are in square brackets] phenylalanine — tyrosine [via liver phenylalanine hydroxylase + tetrahydrobiopterin] —> i.-dopa (l.-dihydroxyphenylalanine) [via tyrosine hydroxylase + tetrahydrobiopterin] —> dopamine (dihydroxyphenylethylamine) [via dopa decarboxylase + pyridoxal phosphate] — norepinephrine (2-hydroxydopamine) [via dopamine [J-hydroxylasc + ascorbate] —> epinephrine (jV-methyl norepinephrine) [via phenylethanolamine jV-methyltransferase + S-adenosylmethionine]. 

Westerink BH, Tuinte MH (1986) Chronic use of intracerebral dialysis for the in vivo measurement of 3,4-dihydroxyphenylethylamine and its metabolite 3,4-dihydroxy-phenylacetic acid. J Neurochem 46 181-185. 

The conversion of tyrosine to 3,4-dihydroxyphenylalanine occurs both in vivo in man (590) and in vitro by the action of tissue tyrosinase (205, 688). Mammals can decarboxylate both tyrosine (402,407) and dihydroxyphenyl-alanine (406), tyrosine decarboxylase and dihydroxyphenylalanine (dopa) decarboxylases being quite distinct and separable (405), though both are dependent on pyridoxal phosphate (73, 758, and review 72). In mammals dihydroxyphenylalanine is the most readily decarboxylated of all amino acids, and it is therefore not unreasonable to assume that this is the substrate normally decarboxylated in adrenaline biosynthesis cf. 74, 75). Support for this concept derives from the fact that both the substrate and the product of the reaction (3,4-dihydroxyphenylethylamine diagram 11) can or do occur in the adrenal (298, 299, 802), and the amine is moreover, like adrenaline and noradrenaline, a normal urinary excretion product (245, 404). 

As three of the four stages in adrenaline biogenesis are thus provisionally established, the remaining stage, introduction of the side-chain hydroxyl, should occur by conversion of dihydroxyphenylethylamine to noradrenaline. There appears to be little information available on this reaction (c/. 195a). 

The relation of many of the simpler alkaloids to the aromatic amino acids is obvious. For example, germinating barley contains (241), besides tyrosine and tyramine, A -methyltyramine, JViV -dimethyltyramine (hordenine), and the trimethylammonium derivative (candicine). In this simple case the. AT-methylated derivatives are known to be derivable from isotopically labeled tyramine (538) and the methyl groups are known to arise from methionine by transmethylation (540, 586). Similarly AT-methyl derivatives of phenylethylamine, 3,4-dihydroxyphenylethylamine, and 3,4,5-trihy-droxyphenylethylamine are well known alkaloids (cf. review, 701). N-Methylated derivatives of tryptamine and hydroxytryptamine equally occur for example, eserine has an obvious relation to 5-hydroxy tryptamine. Methylated derivatives of metabolites of the aromatic amino acids also occur, for example, trigonelline (67), which is the betaine of nicotinic acid, and damascenine is probably similarly related to hydroxyanthranilic acid. 

DA (3,4-dihydroxyphenylethylamine Table 10-1) is the metabolic precursor of NE and Epi it is a central neurotransmitter particularly important in the regulation of movement see Chapters 12, 18, and 20). In the periphery, DA is synthesized in epithelial cells of the proximal tubule and is thought to exert local diuretic and natriuretic effects. DA is a substrate for both MAO and COMT and thus is ineffective when administered orally. Classification of DA receptors is described in Chapters 12 and 20. 

Biomimetic Syntheses of 5,6-Dihydroxyindoles 1 and 2, and Related Derivatives Based on Oxidative Cyclization of 3,4-Dihydroxyphenylethylamines... 

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