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PubMed1979

Stereochemistry and mechanism of reactions catalyzed by indolyl-3-alkane alpha-hydroxylase.

The reaction of tryptamine with indolyl-3-alkane alpha-hydroxylase is shown to remove stereospecifically the pro-S hydrogen at C-2 of the side chain and to give hydroxytryptamine of "R" configuration. The reaction therefore proceeds stereospecifically with net inversion of configuration at C-2 of the tryptamine side chain. In the reaction of L-tryptophan methyl ester, the enzyme also catalyzes stereospecific removal of the pro-S hydrogen at C-3, but the product 3-hydroxytryptophan methyl ester is racemic at C-3. The unreacted tryptophan methyl ester is shown to incorporate solvent hydrogen into the pro-S position at C-3 in an at least partially stereospecific manner, suggesting that the reaction of L-tryptophan methyl ester is reversible. The hydrogens at C-1 of the tryptamine side chain and the alpha-hydrogen of L-tryptophan methyl ester are shown to be retained in the reactions. The results support the notion that the enzyme catalyzes stereospecific 1,4-dehydrogenation of 3-substituted indoles to the coresponding alkylidene indolenines as the primary reaction, followed by stereospecific or nonstereospecific hydration of these intermediates as a secondary process. Substrate specificity studies with a number of tryptophan analogs are in excellent agreement with such a mechanism.

Carbon Radioisotopes↗
PubMed1994

Characterization of a 5-hydroxytryptamine receptor in mouse neuroblastoma N18TG2 cells.

Cyclic AMP formation was found to increase in mouse neuroblastoma N18TG2 cells exposed to 5-hydroxytryptamine (5-HT). This response was concentration-dependent with an EC50 value of 0.22 microM. Tryptamine and other tryptamine-related compounds were also agonists in this assay with a rank order of potency of 5-methoxytryptamine > 5-HT > tryptamine > 2-methyl-5-HT > 5-carboxamidotryptamine >> alpha-methyl-5-HT. (D)-Lysergic acid diethylamide and 2-bromo-lysergic acid diethylamide were partial agonists in this system with maximal responses of 44 and 34%, respectively, compared to 5-HT. 5-HT-stimulated cyclic AMP formation was inhibited by clozapine, mianserin and methiothepin with pA2 values of 6.6, 6.5 and 6.4, respectively. Radioligand binding studies using [125I]iodolysergic acid diethylamide revealed a binding site present at a density of 10.4 fmol/mg of protein, with an affinity for the ligand of 1.18 nM. In competition studies this binding site displayed a pharmacology similar to that defined in studies of cyclic AMP formation. The pharmacological profile of this receptor, characterized by both radioligand binding and functional coupling to adenylyl cyclase, does not correspond to that of any of the currently classified subtypes of 5-HT receptor, but is similar to the 5-HT receptor cloned recently from rat striatum and referred to as the 5-HT6 receptor. The N18TG2 cell line represents a useful model system in which this novel 5-HT receptor may be characterized fully.

Adenylyl Cyclases↗
PubMed1979

Effect of metastatic cancer on platelet monoamine oxidase activity and serotonin metabolism.

Platelet monoamine oxidase (MAO) activity and urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), serotonin, tyramine and tryptamine were measured in patients with a variety of metastatic cancers and in healthy control subjects. The patients with cancer had higher platelet MAO activity and lower urinary excretion of 5-HIAA, sertonin and tyramine than the healthy subjects. The urinary tryptamine excretion was not significantly different in the two groups. At the present time it is unclear if the alterations in platelet MAO activity and monoamine excretion are casually related.

Adult↗
PubMed2004

Expression of a feedback-resistant anthranilate synthase in Catharanthus roseus hairy roots provides evidence for tight regulation of terpenoid indole alkaloid levels.

Different plant species produce a variety of terpenoid indole alkaloids, which are of interest as plant defensive secondary metabolites and as valuable pharmaceuticals. Although significant progress has been made, the mechanisms regulating the levels of this important class of compounds require continued elucidation. Previous precursor feeding studies have indicated that alkaloid accumulation can be improved during the exponential growth phase of hairy root cultures through enhanced tryptophan availability. To test this relationship, transgenic hairy root cultures of Catharanthus roseus were established with a glucocorticoid-inducible promoter controlling the expression of an Arabidopsis feedback-resistant anthranilate synthase alpha subunit. Enzyme assays demonstrated that the Arabidopsis alpha subunit is compatible with the native beta subunit and that anthranilate synthase activity is more resistant to tryptophan inhibition in induced than in uninduced extracts. The metabolic effects of expressing the feedback-resistant anthranilate synthase alpha subunit were also dramatic. Over a 6-day induction period during the late exponential growth phase, tryptophan and tryptamine specific yields increased from almost undetectable levels to 2.5 mg/g dry weight and from 25 microg/g to 267 microg/g dry weight, respectively. The greater than 300-fold increase in tryptophan levels observed in these studies under certain induction conditions compares favorably with the fold increases obtained in previous constitutive expression studies. Despite the large increases in tryptophan and tryptamine, the levels of most terpenoid indole alkaloids were not significantly altered, with the exception of lochnericine, which increased 81% after a 3-day induction period. These results suggest that terpenoid indole alkaloid levels are tightly controlled.

Anthranilate Synthase↗
PubMed1976

Adsorption of tryptophan metabolites from physiological fluids on XAD-2 and determination by single ion monitoring.

Endogenous tryptamine, 5-hydroxytryptamine, indoleacetic acid, 5-hydroxyindoleacetic and tryptophan have been recovered from urine and cerebro-spinal fluid by adsorption on XAD-2 resin (0.3 g). After adsorption of the sample on the resin, desorption with methanol provides a single fraction that contains all of these metabolites. The mass spectra of their pentafluoropropionyl derivatives show prominent ions at m/e 276 and 438 which are characteristic of indoles and 5-hydroxyindoles, respectively, a feature that allows the concurrent determination of all the components of each group by functional group analysis. A method has been developed to carry out single ion monitoring with the peak matching system of an Hitachi RMU-6H mass spectrometer. Identifications are based on the respective Kovats Indices and single ion monitoring of two characteristic ions per compound: tryptophan (m/e 276 and 347); tryptamine (m/e 276 and 289); indoleacetic acid (m/e 276 and 335); 5-hydroxytryptamine (m/e 438 and 451); 5-hydroxyindoleacetic acid (m/e 438 and 497). The method described illustrates the feasibility of assaying biogenic indoleamines and acidic metabolites, as well as their precursor amino acid on a single fraction in contrast to other standard fractionation methods. This is possible even if the mass spectrometer is not equipped with an alternating voltage accelerator provided that it has a peak matcher, although the lack of an alternating voltage accelerator requires two separate injections of the same sample, for quantification and identification; one for the indole profile and another for the 5-hydroxyindole profile. Both profiles can be verified by individual monitoring of the other confirmatory ions. With this method the use of a multiple ion detector would allow a simultaneous determination of all of these metabolites in one gas chromatograph mass spectrometer run.

Adsorption↗
PubMed1977

Effects of 3,4-dimethoxyphenethylamine derivatives on monoamine oxidase.

The cactus alkaloid 3,4-dimethoxyphenethylamine and its naturally occurring N-methylated homologs inhibited the deamination of tyramine and tryptamine by rat brain monoamine oxidase. In contrast, the beta-hydroxylated derivatives of this series failed to inhibit the action of monoamine oxidase on both tyramine and tryptamine.

Animals↗
PubMed1980

New aspects on factors determining the sensitivity of the formaldehyde and glyoxylic acid fluorescence histochemical methods for monoamines.

The fluorophore and fluorescence yield from tryptamine and 3-methoxytyramine in histochemical protein models have been compared in the standard formaldehyde reaction, the acid-catalyzed formaldehyde reaction, the formaldehyde-ozone reaction, and the aluminum-formaldehyde reaction. In the standard formaldehyde reaction both the fluorophore and fluorescence yields are low. However, the other reactions give a dramatic increase in fluorescence intensity (18-20 times) from tryptamine and 3-methoxytyramine whereas only minor changes (up to 100% increase) in fluorophore yield are observed. It is concluded that the relative fluorescence intensity of each fluorophore molecule formed in the three modifications of the formaldehyde reaction is much higher than that of the molecules formed in the standard formaldehyde reaction. It has previously been demonstrated that the fluorophores formed from dopamine in the gaseous formaldehyde and glyoxylic acid reactions have a much higher (10 times) relative fluorescence intensity than the synthetic fluorophores. the prresent experiments show that if the histochemicl models are dissolved in buffer after the reaction and new models are made from this solution, the fluorescence intensity of the fluorophores formed in the reaction is drastically reduced and becomes comparable to that of the synthetic ones. The results of this and our previous studies indicate that hitherto unknown fluorescence enhancing mechanisms play a major role for the fluorescence yield, i.e. the sensitivity, in the various formaldehyde and glyoxylic acid methods. One possible explanation to the high relative fluorescence intensity of the fluorophores formed in the histochemical reactions could be an energy transfer between, e.g. the non-fluorescent intermediary reaction products (the tetrahydro derivatives) and the fluorophores (the dihydroisoquinolines and dihydro-beta-carbolines). Such an energy transfer is probably attenuated in the dissolved models, where th distances betweenm and orientations of the various molecules have been changed.

Dopamine↗
PubMed1987

Simultaneous detection of indoleamines and dopamine in rat dorsal raphe nuclei using specific antibodies.

Using a monoclonal antibody against dopamine and a rabbit antiserum against serotonin, 5-methoxytryptamine or tryptamine, we were able to achieve the simultaneous localization of two amines in glutaraldehyde-fixed sections of rat dorsal raphe nuclei. In this staining procedure, the first antigen was localized using 3,3'-diaminobenzidine (DAB), while the second antigen was stained using the 1-naphthol basic dye (2-NBD) method. The two antigens were localized in different cells or structures. No overlap of the staining was observed, thus indicating that dopamine is not localized with serotonin, 5-methoxytryptamine or tryptamine.

3,3'-Diaminobenzidine↗
PubMed1980

Evaluation of the binding of serotonin by isolated CNS acidic lipids.

Binding of serotonin by rat lipids was examined in an organic solvent-aqueous partition system. Only phospholipids and sulfatide were found to have appreciable activity; this technique was unsuitable for gangliosides due to their poor extractibility. Binding by phospholipid was abolished and that by sulfatide was greatly inhibited by increasing ionic strength in the aqueous phase. At an ionic strength of 0.3 M the apparent affinity of sulfatide for serotonin was about 3 X 10(3) M. Both tryptamine and 5-methoxytryptamine were much more effective than serotonin in inhibiting the binding of radioactive serotonin, suggesting that the observed binding is simply a charge neutralization with little specificity. Binding of serotonin by mixed brain gangliosides was examined in an equilibrium dialysis system. Without adequate precautions, the chemical lability of serotonin was found to produce spurious data when binding was assessed by the distribution of radiolabel. Binding of serotonin by ganglioside was also greatly inhibited by increasing ionic strength: at 0.3 M an apparent affinity of about 10(3) M was found. While dopamine did not inhibit the binding of radioactive serotonin, tryptamine, 5-methoxytryptamine, and serotonin were equally effective inhibitors.

5-Methoxytryptamine↗
PubMed1993

Trace amines and Tourette's syndrome.

There has been considerable interest in recent years in possible neurochemical abnormalities in Tourette's Syndrome (TS). In studies combining neuropsychological and neurochemical measurements, we have investigated the possible roles of trace amines in this disorder. Urinary levels of free beta-phenylethylamine (PEA) and plasma levels of its precursor amino acid phenylalanine were decreased in TS patients when compared to values in normal children. These urinary PEA levels in TS patients were inversely related to several scores from the Tourette's Syndrome Global Scale (TSGS). Further investigation of the group of subjects with low urinary PEA indicated that they also had low levels of MHPG, normetanephrine, 5-HT and m- and p-tyramine. Patients with low PEA were also compared on an extensive battery of neuropsychological measures and observed to perform significantly worse than TS patients with normal urinary PEA levels. Biochemical measurements also suggest a possible abnormality in tryptamine turnover in TS since urinary levels of indole-3-acetic acid (IAA; the acid metabolite of tryptamine) are significantly lower in TS patients than in normal controls.

Biogenic Amines↗
PubMed1988

Kinetics of intraventricularly injected trace amines and their deuterated isotopomers.

Intraventricular injection into the rat brain of four trace amines and a catecholamine resulted in rapid exponential loss of the amines in the first 30 minutes after injection. The half-lives were: phenylethylamine 3.8 min, para-tyramine 5.1 min, meta-tyramine 7.4 min and dopamine 8.0 min. Tryptamine showed a biphasic loss with half-lives of 4.7 min (over the 5 to 10 min period) and 14.1 min (10 to 30 min). The half-lives were substantially increased by deuterium labeling at the alpha carbon position: phenylethylamine 4.8 min, para-tyramine 8.8 min, meta-tyramine 14.1 min, dopamine 13.0 min and tryptamine 6.0 min (5 to 10 min period) and 28.7 min (10 to 20 min). The loss of the amines was reduced by monoamine oxidase inhibition by pargyline hydrochloride and the deuterium isotope effect was abolished. It is noteworthy that the half-life of dopamine was similar to those of the trace amines in this time period and that the trace amine half-lives after i.v. injection was longer than those obtained from measurements of increases of concentrations of endogenous amines after MAOI in vivo and that of dopamine shorter than values calculated from turnover measurements.

Animals↗
PubMed1989

Assay of strictosidine synthase from plant cell cultures by high-performance liquid chromatography.

An HPLC assay is described for the enzyme strictosidine synthase in which the formation of strictosidine and the decrease of tryptamine can be followed at the same time. In cell cultures of Catharanthus roseus significant amounts of strictosidine glucosidase activity were detected. In crude preparations, the strictosidine synthase reaction is therefore best measured by the secologanin-dependent decrease of tryptamine. In this way, the specific synthase activity in a cell free extract was found to be 56 pkat/mg of protein. Inclusion of 100 mM D(+)-gluconic acid-delta-lactone in the incubation mixture inhibited 75% of the glucosidase activity, without inhibiting the synthase activity. The synthase activity was readily separated from the glucosidase activity by gel filtration on Sephadex G-75 or Ultrogel AcA-44. Cell cultures of Tabernaemontana orientalis did not contain measurable amounts of strictosidine glucosidine activity. The specific strictosidine synthase activity was 130-200 pkat/mg of protein during the growth of this cell culture. Strictosidine synthase is stable at -20 degrees C for at least 2 months.

Carbon-Nitrogen Lyases↗
PubMed1990

Sensitivity of tryptophan and related compounds to oxidation induced by lipid autoperoxidation. Application to human serum low- and high-density lipoproteins.

Tryptamine, serotonin and tryptophan are readily oxidized during the Cu2+-catalyzed peroxidation of arachidonic acid (AA) at neutral pH and under certain experimental conditions which determine their relative susceptibility to oxidation. Thus, in AA micelles, fluorescence spectroscopy demonstrates that positively-charged indoles interact with negatively-charged micelles while Trp remains in the aqueous phase. As a result, serotonin and tryptamine are preferentially oxidized. In egg phosphatidylcholine liposomes loaded with AA, the three substrates interact with vesicles and undergo lipid-induced oxidation. EDTA inhibits the formation of thiobarbituric-reactive substances (TBARS) and prevents the indoles from oxidation. Owing to the intricate contact between the lipidic core and the apolipoproteins, the Trp residues of human serum LDL and HDL3 are very rapidly oxidized, i.e., at least one order of magnitude faster than Tyr HDL and Lys LDL, which are believed to be involved in the binding of these lipoproteins to their cell receptors. Cupric ions are rather specific for the lipid-induced autoxidation of Trp residues of lipoproteins whereas in micelles and liposomes, Mn2+ and Fe2+ can lead to TBARS production and to oxidation of indoles. This specificity is surprising considering the known ability of Fe2+ to catalyze LDL modification (measured by TBARS production) during their incubation with various cells. Biological consequences of the easy lipid-induced oxidation of biologically important indoles are discussed.

Humans↗
PubMed1982

Some properties of monoamine oxidase and a semicarbazide sensitive amine oxidase capable of the deamination of 5-hydroxytryptamine from porcine dental pulp.

The deamination of 5-hydroxytryptamine, tryptamine and benzylamine by porcine dental pulp membrane preparations is brought about not only by monoamine oxidase, but also by a clorgyline (and deprenyl) resistant), semicarbazide sensitive enzyme. The semicarbazide sensitive enzyme was also inhibited by aminoguanidine, hydroxylamine and phenylhydrazine, but was not affected to any significant extent by incubation at 50 degrees for up to 100 min. There was, on the other hand, considerable inhibition of monoamine oxidase activity after incubation at this temperature. The semicarbazide sensitive enzyme neither metabolised, nor was inhibited by putrescine or cadaverine. Mixed substrate experiments indicated that 5-hydroxytryptamine and tryptamine interacted at the same catalytic centre on the semicarbazide sensitive enzyme.

Amine Oxidase (Copper-Containing)↗
PubMed1988

Neurochemical changes in rat brain amines after short- and long-term inhibition of monoamine oxidase by a low dose of tranylcypromine.

The effects of short- and long-term administration of a low dose of tranylcypromine on brain and urine levels of several biogenic amines and on brain activity of monoamine oxidases (MAO) A and B were investigated. MAO-A and MAO-B were inhibited by greater than 85% on day 1, and this inhibition continued to increase over the course of the study (42 days). Levels of 5-hydroxytryptamine in brain continued to increase up to day 21 and did not decline from day 21 to day 42, and levels of tranylcypromine itself continued to increase up to day 42. Dopamine concentrations peaked at day 10 and were not significantly different from that value by day 42. Brain levels of tryptamine and beta-phenylethylamine showed dramatic elevations after the first dose of the drug and remained essentially unchanged from those high values throughout the course of the drug treatment. Brain and urine increases in tryptamine and beta-phenylethylamine showed similar patterns, whereas urinary 5-hydroxytryptamine excretion reached maximal levels earlier than did brain levels.

Animals↗
PubMed1976

Comparative effects of four migraine prophylactic drugs on an isolated extracranial artery.

Clonidine and methysergide constrict the rabbit auricular artery by activating smooth muscle alpha-adrenoceptors. Clonidine inhibits and methysergide enhances responses to stimulation of the sympathetic nerves. Both drugs sensitise the artery to a variety of vasoconstrictor stimuli, although not to potassium chloride. This weak generalised sensitisation may depend on clonidine and methysergide themselves being vasoconstrictor since sensitisation after clonidine did not occur when vasoconstriction was abolished with phentolamine. The marked potentiation of 5-HT and tryptamine observed during clonidine perfusion may reflect a property of the tryptamines since it was observed during perfusion with histamine but not when histamine vasoconstriction was abolished with mepyramine. Cyproheptadine and pizotifen neither constrict the artery nor sensitise it to vasoconstrictor agents. They inhibit responses to nerve stimulation, alpha-adrenoceptor agonists, potassium chloride and particularly histamine. Sensitisation of blood vessels reinforced by direct vasoconstriction may contribute to the mechanism of action of clonidine and methysergide in migraine. Conversely, alterations in vascular function may be less important to the antimigraine actions of either cyproheptadine or pizotifen.

Animals↗
PubMed1984

The effect of zimelidine and amitriptyline on the brain concentration of some indolic and phenolic monoamines in the mouse.

The increase in mouse brain tryptamine accumulation rate and 5-hydroxytryptamine (5-HT) concentration and the reduction in 5-hydroxyindole acetic acid concentration observed after zimelidine administration suggest that the treatment reduces the brain tryptophan availability. Amitriptyline produced no significant changes on tryptamine, 5-HT or 5-hydroxyindole acetic acid. Also, zimelidine reduced mouse brain p-tyramine, increased m-tyramine and increased homovanillic acid. Similar effects were observed after amitriptyline administration. The experiments show that both drugs affect dopamine turnover and tyramine concentration in a similar fashion to that observed for the antipsychotic group of drugs, thus suggesting that they may have some antipsychotic effects, especially if administered at the high dose levels. In addition, it may also possess some of the undesirable effects of this group of drugs.

Amitriptyline↗