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PubMed2003

Multiple mechanisms involved in the inhibition of proinflammatory cytokine production from human monocytes by N-(p-coumaroyl)serotonin and its derivatives.

We have reported that N-(p-coumaroyl)serotonin(CS) isolated from safflower oil cake (Carthamus tinctorius L.) inhibits the production of proinflammatory cytokines by endotoxin (LPS)- stimulated human monocytes. In this study, the effects of CS and its three derivatives, N-(trans-cinnamoyl)serotonin (Cin.S), N-(trans-cinnamoyl)tryptamine (Cin.T), and N-(p-coumaroyl)tryptamine (CT) on the production of proinflammatory cytokines were compared. Cin.S possessed radical scavenging activity at a comparable level to CS, while CT and Cin.T exhibited lower activity, suggesting that hydroxyl group in serotonin is essential for the antioxidative activity. CS and CT strongly inhibited the production of proinflammatory cytokines (IL-1alpha, IL-1beta, IL-6, IL-8, and TNF-alpha) from LPS-stimulated human monocytes. However, Cin.S inhibited the production of only IL-1alpha and IL-1beta, and Cin.T inhibited none of these cytokines production. CS and CT markedly inhibited the protein synthesis in monocytes, the inhibitory effect of Cin.S was moderate, and that of Cin.T was quite weak. These results indicate that CS and its derivatives inhibit the production of proinflammatory cytokines through multiple mechanisms.

Antioxidants↗

PubMed2001

Characterization of 5-HT receptors in the parasitic nematode, Ascaris suum.

The pharmacological profiles of the 5-hydroxytryptamine (5-HT) receptors on Ascaris suum pharyngeal and somatic body wall muscles were investigated. The mechanisms involved following activation of these receptors were also studied. 5-HT activated and maintained pumping in isolated pharynxes with an EC-50 value of 44+/-1.7 microM. The 5-HT agonists, tryptamine, sumatriptan 8-OH-DPAT and 5-carboxyamidotryptamine all failed to stimulate pumping. The 5-HT2 antagonist, ketanserin, initially excited and then inhibited pumping while the 5-HT3 antagonist, ondansetron, had no effect. 5-HT and 5-HT agonists, 8-OH-DPAT, 5-carboxyamidotryptamine, alpha-methyl-5-HT and tryptamine all inhibited ACh-induced contractions of a somatic body wall muscle strip. Ketanserin partially blocked the inhibitory effect of alpha-methyl-5-HT and ACh-induced contractions while the 5-HT uptake blocker, fluoxetine, potentiated the effect of 5-HT on ACh-induced contractions. Basal levels of cAMP, 1540+/-232 pmol/mg, in pharyngeal muscle and 1721+/-134 pmol/mg, somatic body wall muscle, were both increased by forskolin. 5-HT had no effect on pharyngeal muscle cAMP levels but raised cAMP levels in somatic body wall muscle, e.g. 100 micron 5-HT, raised the level to 2851+/-212 pmol/mg and 1000 microM raised levels to 4578+/-1234 pmol/mg. 5-HT, 1000 microM, increased inositol phosphate levels in pharyngeal muscle. These results provide some evidence for a 5-HT2-like receptor on pharyngeal muscle. In contrast, the situation on somatic body wall muscle is more confusing since the pharmacological profile partly indicates a 5-HT2-like receptor but this receptor is linked to a rise in cAMP levels. Further studies are required to resolve the position but they must be based on the rational design of ligands specifically for nematode 5-HT receptors and not simply using ligands developed for the classification of mammalian 5-HT receptors. Such a design must take into account data from molecular biology studies of nematode 5-HT receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2005

Synthesis, characterization, crystal structure, and electrochemical, photophysical, and protein-binding properties of luminescent rhenium(I) diimine indole complexes.

We report the synthesis, characterization, and photophysical and electrochemical properties of a series of luminescent rhenium(I) diimine indole complexes, [Re(N-N)(CO)3(L)](CF3SO3) (N-N = 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4-phen), L = N-(3-pyridoyl)tryptamine (py-3-CONHC2H4-indole) (1a), N-[N-(3-pyridoyl)-6-aminohexanoyl]tryptamine, (py-3-CONHC5H10CONHC2H4-indole) (1b); N-N = 1,10-phenanthroline (phen), L = py-3-CONHC2H4-indole (2a), py-3-CONHC5H10CONHC2H4-indole (2b); N-N = 2,9-dimethyl-1,10-phenanthroline (Me2-phen), L = py-3-CONHC2H4-indole (3a), py-3-CONHC5H10CONHC2H4-indole (3b); N-N = 4,7-diphenyl-1,10-phenanthroline (Ph2-phen), L = py-3-CONHC2H4-indole (4a), py-3-CONHC5H10CONHC2H4-indole (4b)), and their indole-free counterparts, [Re(N-N)(CO)3(py-3-CONH-Et)](CF3SO3) (py-3-CONH-Et = N-ethyl-(3-pyridyl)formamide; N-N = Me4-phen (1c), phen (2c), Me2-phen (3c), Ph2-phen (4c)). The X-ray crystal structure of complex 3a has also been investigated. Upon irradiation, most of the complexes exhibited triplet metal-to-ligand charge-transfer (3MLCT) (d pi(Re) --> pi*(diimine)) emission in fluid solutions at 298 K and in low-temperature glass. However, the structural features and long emission lifetimes of the Me4-phen complexes in solutions at room temperature suggest that the excited state of these complexes exhibited substantial triplet intraligand (3IL) (pi --> pi*) (Me4-phen) character. The binding interactions of these complexes to indole-binding proteins including bovine serum albumin and tryptophanase have been examined.

Crystallization↗

PubMed1997

Metabolism studies of indole derivatives using a staurosporine producer, Streptomyces staurosporeus.

From a tryptophan metabolic study, 3-(hydroxyacetyl)indole, indole-3-carboxaldehyde, and o-aminobenzoic acid were obtained as tryptophan metabolites from a staurosporine (1) producer, Streptomyces staurosporeus. A new tryptamine metabolite, (3aR,8aS)-1-acetyl-1,2,3,3a,8,8a-hexahydropyrrolo[2,3- b]indol-3a-ol (2), was isolated along with Nb-acetyltryptamine using S. staurosporeus fed with tryptamine. The unusual compound 2 was proposed as a further metabolite of Nb-acetyltryptamine through an enzymatic oxidative cyclization. Examination of the metabolites from the feeding of 5- and 6-fluorotryptamines using the same microorganism afforded the two novel compounds 3 and 4 as the 5- and 6-fluoro derivatives of 2. However, 5-hydroxytryptamine failed to generate the 5-hydroxy derivative of 2. Indole-ring-substituted metabolites of staurosporine (1) were not observed.

Culture Media↗

PubMed2002

A versatile linkage strategy for solid-phase synthesis of N,N-dimethyltryptamines and beta-carbolines.

Various tryptamines are captured by a vinylsulfonylmethyl polystyrene resin, generating a safety-catch linkage. Beta-carbolines can be formed from 4 by a Pictet-Spengler reaction with the introduction of R(1). Tryptamine 4 can also be derivatized by acylation or copper-mediated coupling to introduce R(2). If X = Br, Suzuki coupling can be used to introduce R(3). After derivatization, the indole derivatives are activated with methyl iodide and released under mild basic condition. [reaction: see text]

Carbolines↗

PubMed2006

Trace amine-associated receptors and their ligands.

Classical biogenic amines (adrenaline, noradrenaline, dopamine, serotonin and histamine) interact with specific families of G protein-coupled receptors (GPCRs). The term 'trace amines' is used when referring to p-tyramine, beta-phenylethylamine, tryptamine and octopamine, compounds that are present in mammalian tissues at very low (nanomolar) concentrations. The pharmacological effects of trace amines are usually attributed to their interference with the aminergic pathways, but in 2001 a new gene was identified, that codes for a GPCR responding to p-tyramine and beta-phenylethylamine but not to classical biogenic amines. Several closely related genes were subsequently identified and designated as the trace amine-associated receptors (TAARs). Pharmacological investigations in vitro show that many TAAR subtypes may not respond to p-tyramine, beta-phenylethylamine, tryptamine or octopamine, suggesting the existence of additional endogenous ligands. A novel endogenous thyroid hormone derivative, 3-iodothyronamine, has been found to interact with TAAR1 and possibly other TAAR subtypes. In vivo, micromolar concentrations of 3-iodothyronamine determine functional effects which are opposite to those produced on a longer time scale by thyroid hormones, including reduction in body temperature and decrease in cardiac contractility. Expression of all TAAR subtypes except TAAR1 has been reported in mouse olfactory epithelium, and several volatile amines were shown to interact with specific TAAR subtypes. In addition, there is evidence that TAAR1 is targeted by amphetamines and other psychotropic agents, while genetic linkage studies show a significant association between the TAAR gene family locus and susceptibility to schizophrenia or bipolar affective disorder.

Amino Acids↗

PubMed1982

Differential energy requirements for platelet responses. A simultaneous study of aggregation, three secretory processes, arachidonate liberation, phosphatidylinositol breakdown and phosphatidate production.

Previous studies have indicated different energy requirements for some platelet responses; these differences could, however, be due to inadequate methodology and differences in platelet preparation. The present study describes the effect of decreasing ATP availability on seven platelet responses measured in gel-filtered human platelets. The cells, prelabelled with 5-hydroxy[(3)H]tryptamine, [(3)H]- or [(14)C]adenine, [(32)P]P(i) or [(3)H]arachidonate, were incubated with antimycin A and 2-deoxy-d-glucose. Platelet responses induced by thrombin and collagen (secretion only), level of metabolic ATP and the adenylate energy charge (AEC) were determined at various times during incubation. Platelet aggregation was rapidly inhibited after a lag of 5-15 min and with 50% inhibition at AEC = 0.55-0.60. Secretion of 5-hydroxy[(14)C]tryptamine and ATP + ADP from dense granules and of fibrinogen and beta-thromboglobin from alpha-granules were inhibited in parallel, without a lag and with 50% inhibition at AEC = 0.65-0.70. The inhibition of secretion of platelet factor 4 from the alpha-granules followed another pattern with 50% inhibition at AEC = 0.70-0.80. Breakdown of [(3)H]-phosphatidylinositol, formation of [(3)H]- and [(32)P]-phosphatidate, liberation of [(3)H]arachidonate and secretion of acid hydrolases were inhibited in parallel and inhibition was present at the start of incubation with 50% inhibition at AEC = 0.80-0.87. These results suggest that the responses have different energy requirements, increasing in the order: aggregation < dense granule and alpha-granule secretion < acid hydrolase secretion, phosphatidylinositol breakdown, phosphatidate formation and arachidonate liberation. The powerful inhibition of phosphatidylinositol breakdown by metabolic inhibitors suggests that energy-requiring steps are involved in the activation of phospholipase C.

Antimycin A↗

PubMed1990

Ethanol inhibits thrombin-induced secretion by human platelets at a site distinct from phospholipase C or protein kinase C.

Ethanol is known to inhibit the activation of platelets in response to several physiological agonists, but the mechanism of this action is unclear. The addition of physiologically relevant concentrations of ethanol (25-150 mM) to suspensions of washed human platelets resulted in the inhibition of thrombin-induced secretion of 5-hydroxy[14C]tryptamine. Indomethacin was included in the incubation buffer to prevent feedback amplification by arachidonic acid metabolites. Ethanol had no effect on the activation of phospholipase C by thrombin, as determined by the formation of inositol phosphates and the mobilization of intracellular Ca2+. Moreover, ethanol did not interfere with the thrombin-induced formation of diacylglycerol or phosphatidic acid. Stimulation of platelets with phorbol ester (5-50 nM) resulted in 5-hydroxy[14C]tryptamine release comparable with those with threshold doses of thrombin. However, ethanol did not inhibit phorbol-ester-induced secretion. Ethanol also did not interfere with thrombin- or phorbol-ester-induced phosphorylation of myosin light chain (20 kDa) or a 47 kDa protein, a known substrate for protein kinase C. By electron microscopy, ethanol had no effect on thrombin-induced shape change and pseudopod formation, but prevented granule centralization and fusion. The results indicate that ethanol does not inhibit platelet secretion by interfering with the activation of phosphoinositide-specific phospholipase C or protein kinase C by thrombin. Rather, the data demonstrate an inhibition of a Ca2(+)-mediated event such as granule centralization.

Adenosine Diphosphate↗

PubMed1995

5-hydroxytryptamine stimulates glucose transport in cardiomyocytes via a monoamine oxidase-dependent reaction.

This study deals with the effect of 5-hydroxytryptamine (5-HT; serotonin) on glucose transport in isolated rat cardiac myocytes. In these cells, 5-HT (10-300 microns), as well as tryptamine, 5-methoxytryptamine and dopamine, elicited a 3-5 fold increase in glucose transport, as compared with control. This effect was maximal after 90 min, and was concomitant with a 1.8- and 1.5-fold increase in the amounts of glucose transporters GLUT1 and GLUT4 at the cell surface of the cardiomyocytes, as determined by using the photoaffinity label 3H-2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]-1,3-bis-(D-manno s-4-yl) propyl-2-amine (3H-ATB-BMPA). In contrast, 3-3000 microM of the selective 5-HT receptor agonists 5-carboxyamido-tryptamine, alpha-methyl-serotonin, 2-methyl-serotonin or renzapride failed to stimulate glucose transport. The effect of 5-HT was not affected by (i) the 5-HT receptor antagonists methysergide (1 microM), ketanserin (1 microM), cyproheptadine (1 microM), MDL 72222 (1 microM) or ICS 205-930 (3 microM), nor by (ii) the adrenergic receptor antagonists prazosin (1 microM), yohimbine (1 microM) or propranolol (5 microM), nor by (iii) the dopaminergic antagonists SCH 23390 (1 microM) or haloperidol (1 microM). The monoamine oxidase inhibitors clorgyline (1 microM) and tranylcypromine (1 microM) completely suppressed the effect of 5-HT, whereas the control and insulin-stimulated rates of glucose transport were unaffected. Addition of catalase or glutathione diminished the 5-HT-dependent stimulation of glucose transport by 50%; these two factors are known to favour the degradation of H2O2 (which can be formed during the deamination of amines by monoamine oxidases). Glutathione also depressed the stimulatory action of exogenously added H2O2 (20 microM) by 30%. Furthermore, in cells treated with 5_HT, a time-dependent accumulation of 5-hydroxy-1H-indol-3-ylacetic acid (a product of 5-HT metabolism via monoamine oxidases) was observed, which paralleled the changes in glucose transport. In conclusion, the stimulation of glucose transport by 5-HT in cardiomyocytes is not mediated by a 5-HT1, 5-HT2, 5-HT3 or 5-HT4 receptor, nor by an adrenergic or dopaminergic receptor, but is likely to occur through the degradation of by a monoamine oxidase and concomitant formation of H2O2.

Adrenergic Antagonists↗

PubMed1991

Thermospray Liquid Chromatography/Mass Spectrometry (TSP LC/MS) Analysis of the Alkaloids from Cinchona in vitro Cultures.

The alkaloids from CINCHONA LEDGERIANA shoot cultures and from CINCHONA ROBUSTA shoot cultures and a compact globular structure (CGS) culture were analyzed by thermospray liquid chromatography/mass spectrometry (TSP LC/MS). Because of the relative stability of the alkaloids under TSP discharge ionization conditions, a protonated molecule was observed in the mass spectra with hardly any fragmentation. When the reference compounds were available, the knowledge of the molecular mass and of the retention time was sufficient to identify most of the alkaloids. HPLC with UV photodiode-array detection complemented LC/MS perfectly by providing information about the aromatic part of the alkaloids (structure and substitution pattern). New alkaloids detected in CINCHONA IN VITRO cultures were 5-methoxytryptamine and corynantheal. In order to determine whether 5-methoxytryptamine was a precursor of the methoxylated quinolines, this indole was incubated with secologanin and several CINCHONA ROBUSTA crude protein extracts. Under all conditions tested, the coupling of 5-methoxytryptamine with secologanin remained unsuccessful. Only tryptamine condensed with secologanin to yield strictosidine. These results indicate that CINCHONA cells are able to methoxylate simple indoles like tryptamine and that 5-methoxytryptamine is very likely not used for the subsequent biosynthesis of the methoxylated quinolines.

Journal Article↗

PubMed1981

Effect of L-tryptophan injection in rats on some enzymes of amino acid metabolism in liver. I. In vitro studies of the effect of L-tryptophan and its metabolites on the extramitochondrial L-alanine: 2-ketoglutaric aminotransferase.

Fed and fasted rats were injected with L-tryptophan (12.5 mg/100 g body weight) and the specific activities of L-glutamic: NAD oxidoreductase (deaminating) (EC 1.4.1.2) (GDH), L-aspartic-2-ketoglutaric aminotransferase (EC 2.6.1.1) (GOT) and L-alanine-2-ketoglutaric aminotransferase (EC 2.6.1.2) (GPT) from hepatic mitochondria and cytosol were compared. L-tryptophan results in a decrease of mitochondrial GDH activity by 22% and of cytosolic GPT and GOT by 42% and 38% respectively in the liver of fasted rats. Xanthurenate is a potent inhibitor of purified extramitochondrial GPT, whereas anthranilate and quinolinate are less potent inhibitors. L-tryptophan, 5-OH-tryptophan and indole exert a slight inhibition. Kynurenine, 5-OH-tryptamine, tryptamine, picolinic acid, nicotinic acid and indoloacetic acid do not show any inhibition of GPT. It is suggested that L-tryptophan injection inhibits extramitochondrial GPT by its transformation to xanthurenate and anthranilate.

Alanine Transaminase↗

PubMed1998

Chemistry and pharmacology of hallucinogens, entactogens and stimulants.

Amphetamines, tryptamines, phencyclidines, tetrahydrocannabinol and substances of the ecstasy group are characterized as stimulants, hallucinogens and entactogens. The various effects of each group and their mode of action in different transmitter systems are described. 28 new compounds of the amphetamine and tryptamine series has been calculated, which exceed the hallucinogenic effects of mescaline. The different pathways of the metabolism of MDMA (ecstasy) and MDE in humans may probably explain their individual effects.

3,4-Methylenedioxyamphetamine↗

PubMed1998

Rabbit lung indolethylamine N-methyltransferase. cDNA and gene cloning and characterization.

Indolethylamine N-methyltransferase (INMT) catalyzes the N-methylation of tryptamine and structurally related compounds. This reaction has been studied because of its possible role in the in vivo synthesis of psychoactive compounds or neurotoxins and has been characterized biochemically in preparations of rabbit lung. Therefore, we set out to purify rabbit lung INMT, to clone and express its cDNA, and to clone and structurally characterize its gene as steps toward understanding the function and regulation of this enzyme. Rabbit lung INMT was purified and partial amino acid sequence was obtained. A polymerase chain reaction-based approach was then used to clone a rabbit lung INMT cDNA with a 792-base pair open reading frame that encoded a 263-amino acid protein with a predicted molecular mass of 29 kDa. When the cDNA was expressed in COS-1 cells, the encoded protein catalyzed the methylation of tryptamine and structurally related compounds, and was inhibited by two products of the reaction, S-adenosyl-L-homocysteine (AdoHcy) and N,N-dimethyltryptamine, as well as antimigraine drugs that are structurally related to N,N-dimethyltryptamine. Northern blot analysis demonstrated the presence of 2.0-kilobase mRNA species in rabbit lung, liver and, at lower levels, in brain. The cDNA was then used to clone the rabbit INMT gene. That gene had three exons and was structurally similar to the genes for nicotinamide N-methyltransferase and phenylethanolamine N-methyltransferase in several species. Cloning and expression of a rabbit lung INMT cDNA and cloning of the rabbit INMT gene represent important steps toward determination of the function and regulation of this mammalian methyltransferase enzyme.

Amino Acid Sequence↗

PubMed2005

Potentially hallucinogenic 5-hydroxytryptamine receptor ligands bufotenine and dimethyltryptamine in blood and tissues.

Bufotenine and N,N-dimethyltryptamine (DMT) are hallucinogenic dimethylated indolethylamines (DMIAs) formed from serotonin and tryptamine by the enzyme indolethylamine N-methyltransferase (INMT) ubiquitously present in non-neural tissues. In mammals, endogenous bufotenine and DMT have been identified only in human urine. The DMIAs bind effectively to 5HT receptors and their administration causes a variety of autonomic effects, which may reflect their actual physiological function. Endogenous levels of bufotenine and DMT in blood and a number of animal and human tissues were determined using highly sensitive and specific quantitative mass spectrometric techniques. A new finding was the detection of large amounts of bufotenine in stools, which may be an indication of its role in intestinal function. It is suggested that fecal and urinary bufotenine originate from epithelial cells of the intestine and the kidney, respectively, although the possibility of their synthesis by intestinal bacteria cannot be excluded. Only small amounts of the DMIAs were found in somatic or neural tissues and none in blood. This can be explained by rapid catabolism of the DMIAs by mitochondrial monoamino-oxidase or by the fact that the dimethylated products of serotonin and tryptamine are not formed in significant amounts in most mammalian tissues despite the widespread presence of INMT in tissues.

Animals↗

PubMed1996

Urinary excretion of tetrahydro-beta-carbolines relating to ingestion of alcoholic beverages.

Tetrahydro-beta-carbolines, formed from aldehydes and tryptamine, have been suggested as potential biochemical markers for alcoholism. The excretion of 1-methyl-1,2,3,4-tetrahydro-beta-carboline (MTBC) and 1,2,3,4-tetrahydro-beta-carboline (TBC) in human urine was studied to assess their possible origin. In urine collected after a drinking party, MTBC and TBC were excreted in significantly higher concentrations compared with sobriety. MTBC and TBC were contained in beer and wine at ng/ml levels, but not in distillate alcoholic beverages such as whisky, brandy, gin, etc. The urinary excretion of MTBC and TBC was elevated after drinking beer, whereas no change was observed after drinking whisky. When a human subject was orally administered with deuterated L-tryptophan together with drinking whisky, deuterated tryptamine was increasingly excreted in urine. However, no increase was found in urinary deuterated MTBC. These results indicate that the urinary excretion of MTBC and TBC associated with alcohol ingestion does not imply promotion of their in vivo formation, but the exogenous supply of MTBC and TBC by drinking alcoholic beverages containing them.

Adolescent↗

PubMed2005

Wound-inducible biosynthesis of phytoalexin hydroxycinnamic acid amides of tyramine in tryptophan and tyrosine decarboxylase transgenic tobacco lines.

The wound-activated biosynthesis of phytoalexin hydroxycinnamic acid amides of tyramine was compared in untransformed and transgenic tobacco (Nicotiana tabacum) lines that express tryptophan decarboxylase (TDC), tyrosine decarboxylase (TYDC), or both activities. Transgenic in vitro-grown tobacco lines expressing TDC activity accumulated high levels of tryptamine but not hydroxycinnamic amides of tryptamine. In contrast, transgenic tobacco lines expressing TYDC accumulated tyramine as well as p-coumaroyltyramine and feruloyltyramine. The MeOH-soluble and cell wall fractions showed higher concentrations of wound-inducible p-coumaroyltyramine and feruloyltyramine, especially at and around wound sites, in TYDC and TDC xTYDC tobacco lines compared to wild-type or TDC lines. All the enzymes involved in the biosynthesis of hydroxycinnamic acid amides of tyramine were found to be similarly wound inducible in all tobacco genotypes investigated. These results provide experimental evidence that, under some circumstances, TYDC activity can exert a rate-limiting control over the carbon flux allocated to the biosynthesis of hydroxycinnamic acid amides of tyramine.

Amides↗

PubMed1966

Metabolism of tryptophan in petioles of coleus.

Auxin precursors retard abscission when applied to debladed petioles of Coleus blumei Benth. The d and l forms of tryptophan are equally effective in retarding abscission. Tryptamine is more effective than is tryptophan. Both compounds apparently are converted to auxin through an aldehyde intermediate. The evidence presented suggests that a major pathway of tryptophan metabolism proceeds through tryptamine, as can be demonstrated by the use of amine oxidase inhibitors in the petiole tissue. Cell free preparations of the tissues metabolize tryptophan-1-(14)C with the release of carbon dioxide. The rate of tryptophan mtabolism in abscission tissue is 5 times that in distal petiole tissue. Radioactivity is associated with basic indole conversion products as well as with neutral and acidic fractions. The radioactivity is most concentrated in the neutral fraction. The results indicate that the Coleus petiole itself is capable of producing auxin.

Journal Article↗

PubMed1978

Indole-3-acetic Acid Synthesis in Tumorous and Nontumorous Species of Nicotiana.

The synthesis of indole-3-acetic acid (IAA) in the enzyme extracts of Nicotiana glauca, Nicotiana langsdorffii, their F1 hybrid, their amphidiploid hybrid, and the nontumorous mutant of the hybrid was investigated. Tryptamine, a possible precursor of IAA biosynthesis in Nicotiana tabacum, was not found in the callus tissue of N. glauca, N. langsdorffii, and their F1 hybrid.In petiole slices, the synthesis of IAA progressively increased during 5 hours of incubation in [(14)C]tryptophan. The rate of synthesis was about equal in the hybrid and N. langsdorffii but lower in N. glauca on either a cell or fresh weight basis. It was also found that tryptophan was about 25 times more efficient than tryptamine in promoting synthesis of IAA in petiole slices.It was found that indoleacetaldehyde oxidase, indoleacetaldehyde reductase, and tryptophan aminotransferase activities were present in all of the species examined; however, tryptophan decarboxylase activity was not found. The tryptophan aminotransferase activity in N. glauca, N. langsdorffii, and the nontumorous mutant required alpha-ketoglutaric acid and pyridoxal 5-phosphate whereas the addition of pyridoxal 5-phosphate seemed not to increase the enzyme activity in tumor plants.The tryptophan aminotransferase in the amphidiploid hybrid was partially purified by acetone precipitation. The enzyme activity had a temperature optimum at 49 C and a pH optimum at 8.9. It is suggested that there is an indolepyruvic acid pathway in the synthesis of IAA in the Nicotiana species examined.

Journal Article↗