5-Hydroxytryptophan 5HTP

FIGURE 5—34. Serotonin (5-hydroxytryptamine [5HT ) is produced from enzymes after the amino acid precursor tryptophan is transported into the serotonin neuron. The tryptophan transport pump is distinct from the serotonin transporter (see Fig. 5—35). Once transported into the serotonin neuron, tryptophan is converted into 5-hydroxytryptophan (5HTP) by the enzyme tryptophan hydroxylase (TryOH) which is then converted into 5HT by the enzyme aromatic amino acid decarboxylase (AAADC). Serotonin is then stored in synaptic vesicles, where it stays until released by a neuronal impulse. 

Fig. 6.12. Chromatography of 3H-labelled extracted products following incubation of homogenates of Hymenolepis diminuta in [3H]tryptophan 5HT, 5-hydroxytryptamine 5HTP, 5-hydroxytryptophan TRY, tryptophan or, origin fr, solvent front. The data were obtained by subtracting the radioactivity in boiled homogenates (blanks) from that in unboiled homogenates. Radiolabelled tryptophan was metabolised in the latter to [3H]5HTP and [3H]5HT. (After Ribeiro Webb, 1983a.)...

MD, 3-0-methyldopa 5HTP, 5-hydroxytryptophan HVA, homovanillic acid 5HIAA, 5-hydroxyindoleacetic acid. 

MD, 3-0-methyldopa 5HTP, 5-hydroxytryptophan NE, norepinephrine E, epinephrine DA, dopamine NMN, nor-metanephrine 3MT, 3-methoxytyramine VMA, vanillylmandelic acid 5HT, serotonin HVA, homovanillic acid 5HIAA, 5-hydroxyindoleacetic acid VIA, vanillactic acid. 

The following abbreviations are used 5HTP, 5-hydroxytryptophan 5HIAA, 5-hydroxyindoleacetic acid MAO, monoamine oxidase DPN, diphosphopyridine nucleotide ATP, adeno.sine triphosphate Dopa, 3,4-dihydroxyphenylalanine. 

A, adrenaline COMT, catechol-O-methyl transferase CSF, cerebrospinal fluid DA, 3,4-dihydroxyphenylethylamine (dopamine) Dopa, 3,4-dihydroxyphenylalanine 5HIAA, 5-hydroxyindoleacetic acid 5HT, 5-hydroxytryptamine (serotonin) 5HTP, 5-hydroxytryptophan HVA, 3-methoxy-4-hydroxyphenylacetic acid (homovanillic acid) MAO, monoamine oxidase MAOI, monoamine oxidase inhibitor MHPG,... 

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