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PubMed1983

In vivo conversion of tryptophan to nicotinic acid in rats studied by simultaneous incorporation of [3H]-tryptophan and [14C]-nicotinic acid into liver NAD and NADP.

This study was carried out with three groups of weanling rats. One group was fed a high-protein (20%) diet, another group a low-protein (2.5%) diet, the third group a high-protein diet in restricted amounts. After 4 weeks of feeding, rats were injected simultaneously with L-[G-3H]-tryptophan and [carboxyl-14C]-nicotinic acid. The ratio of incorporation of [3H]-tryptophan to that of [14C]-nicotinic acid into liver NAD and NADP was found to be higher in protein-restricted rats. On the other hand, the ratio was found to be reduced in diet-restricted group of rats compared with ad libitum fed or low-protein diet fed groups. These results suggest that the efficiency of conversion of tryptophan to NAD is increased in protein deficiency, but reduced in the diet restriction. These observations are in line with our earlier findings on the changes in liver quinolinate phosphoribosyltransferase (EC 2.4.2.19) activity following feeding of low-protein or restricted diets. It is suggested that this technique of measuring the incorporation of two isotopes from the substrates labelled with two different isotopes can be conveniently used as a tool to measure the relative contribution of tryptophan and nicotinic acid to the synthesis of nicotinamide nucleotides.

Animals↗
PubMed1988

HPLC assays of 5-HIAA and tryptophan in cerebrospinal fluid and 5-HT and tryptophan in blood: a methodological study with clinical applications.

HPLC methods were developed for the assay of 5-hydroxy-tryptamine (5-HT) and tryptophan in blood after a simple precipitation step, and 5-hydroxy-indolamine acetic acid (5-HIAA) and tryptophan in CSF by direct injection of CSF. Using these methods, CSF and blood contents were studied in drug-free volunteers and patients treated with tricyclic antidepressant (TCA) drugs. Previously reported variations in the CSF concentrations of 5-HIAA with sex and age were confirmed. No significant difference between patients and healthy subjects were seen in the concentrations of tryptophan in blood or CSF, which were significantly positively intercorrelated. There was no intercorrelation between the concentrations of tryptophan and 5-HIAA in CSF. Highly significant differences between patients and healthy subjects in the platelet-content of 5-HT could be ascribed to the TCA medication. Three TCA drugs, amitriptyline, clomipramine, and imipramine, were compared regarding influence on the platelet-content of 5-HT. Patients treated with clomipramine were found to have considerably lower 5-HT values than imipramine- and amitriptyline-treated patients. A logarithmic model indicated a positive correlation between the two serotonin markers studied, i.e., the amount of platelet-bound 5-HT and the CSF concentrations of 5-HIAA.

Adult↗
PubMed1984

Enzymatic dehydrogenation of tryptophan residues of human globins by tryptophan side chain oxidase II.

Enzymatic dehydrogenation of tryptophan residues in human alpha- and beta-globins has been demonstrated with tryptophan side chain oxidase II, a hemoprotein from Pseudomonas. In 1 M ammonium acetate, pH 4, the enzyme catalyzed the conversion of Trp-14 of alpha-globin to alpha, beta-dehydro-Trp. Under identical conditions, Trp-15 of beta-globin was converted to alpha, beta-dehydro-Trp, whereas Trp-37 was unmodified. No modification was obtained in 0.4% sodium dodecyl sulfate or 8 M urea. The dehydrogenase component of tryptophan side chain oxidase II was also active toward globins in the presence of ferricyanide, whereas tryptophan side chain oxidase I was inert. Upon analyses of the tryptic fragments of the modified beta-globin, two forms of alpha, beta-dehydro-Trp-15 distinguishable by ultraviolet absorption and fluorescence were identified. Each of them rapidly equilibrated with another form on irradiation at 300-380 nm. We tentatively assigned them to two isomers of alpha, beta-dehydro-Trp distinguishable by the configuration around its beta-carbon atom. alpha, beta-Dehydro-Trp in globins and certain polypeptides used herein showed a blue fluorescence at 420 nm. In [alpha, beta-dehydro-Trp 15]beta-globin, the fluorescence was exceptionally intense, the fluorescence yield being comparable to that of NADH. From several lines of evidence, the result was ascribed to the excitation energy transfer from Trp-37 to alpha, beta-dehydro-Trp-15 in the modified beta-globin.

Globins↗
PubMed1982

Interactions between tryptophan and multilamellar liposomes. Effect of n-butanol on tryptophan fluorescence.

The fluorescence of indole ring of tryptophan is sensitive to the characteristics of the solvent in which it is located. So that is can be used as a probe of its microenvironment. In the present report we have studied fluorescence changes of tryptophan molecule located in multilamellar liposome of dipalmitoyl-lecithin (DPL). The temperature dependence of tryptophan fluorescence intensity shows increase related to the phase changes in DPL-liposomes. n-Butanol, a fluidizing agent, induces a linear dependence of tryptophan fluorescence from temperature.

1-Butanol↗
PubMed1980

A novel synthesis of 2-thioether derivatives of tryptophan. Covalent binding of tryptophan to cysteine sulfhydryl groups in peptides and proteins.

The reaction of L-3a-hydroxy-1,2,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid (Hpi) with methanethiol, ethanethiol, mercaptoethanol or 3-mercaptopropionic acid in warm aqueous acetic acid gives the corresponding 2-thioether derivatives of tryptophan in 50--80% yield (based on Hpi). Better yields may be obtained in 25% trifluoroacetic acid at room temperature. Cysteine reacts with Hpi to give the double amino acid 2-(L-3-alanylthio)-L-tryptophan (tryptathionine), which is a constituent of the highly poisonous cyclopeptides of Amanita phalloides, such as phalloidin. Reaction of a moderate excess of Hpi with cysteine-SH groups of a tripeptide (glutathione) and a protein (reduced ribonuclease) has also been effected, giving the respective S-tryptophanylated peptide or protein. In both cases, reaction occurred specifically with the -SH groups of cysteine and virtually quantitative covalent binding of tryptophan was verified. The extent of the reaction is easily quantitated by spectrophotometry or by amino acid analysis of the content of oxindolylalanine in the hydrolysate with hot 3-N p-toluenesulfonic acid of the S-tryptophanylated peptide or protein. The reaction should be useful in the field of peptide synthesis, providing a simple method for establishing a cross-link between tryptophan and cysteine, as a basic step in the chemical synthesis of toxic peptides of Amanita phalloides.

Amino Acids↗
PubMed1997

Tryptophan, Tryptophan-Leucine, and BSA Adsorption at an Oil-Water Interface

Adsorption of the amino acid tryptophan, the peptide tryptophan-leucine and the protein bovine serum albumin (BSA) at buffered water-oleyl alcohol interfaces has been studied by ellipsometry. Tryptophan-leucine solutions showed a systematic change in ellipticity with concentration indicating an adsorption of 0.5 mg/m2 for a solution concentration of 1 g/L and evidence of saturation at that concentration. BSA showed an adsorption of 0.45 mg/m2 for a concentration of 3.5 g/L with no sign of saturation. There appeared to be little adsorption of tryptophan at the interface.

Journal Article↗
PubMed1999

Contribution of serum albumin to the transport of orally administered L-tryptophan into liver of rats with L-tryptophan depletion.

The role of serum albumin in the transport of orally administered L-tryptophan (Trp) into rat tissues was examined using analbuminemic and Sprague-Dawley (SD) rats with and without alpha-methyl-DL-tryptophan (AMT)-induced Trp depletion. Trp was orally administered to rats 16 h after AMT or 0.85% NaCl administration, when liver tryptophan 2,3-dioxygenase and protein synthetic activities in AMT-treated rats were similar to those of 0.85% NaCl-treated rats. After oral Trp administration, regardless of the presence or absence of Trp depletion, free serum Trp concentrations were similar in the analbuminemic and SD rats, while total serum Trp concentrations were lower in analbuminemic rats than in SD rats. Although liver, brain, and muscle Trp concentrations after oral Trp administration under Trp depletion were lower in analbuminemic rats than in SD rats, the ratio of the liver Trp concentration in analbuminemic rats to that in SD rats was smaller than that of the brain or muscle Trp concentration. These results suggest that variations in serum albumin levels could affect the transport of orally administered Trp into the liver of rats with Trp depletion.

Administration, Oral↗
PubMed1982

Effects of chronic methamphetamine administration on tryptophan hydroxylase activity, [3H]serotonin synaptosomal uptake, and serotonin metabolism in rat brain following systemic tryptophan loading.

Chronic administration of methamphetamine (20 mg/kg, i.p., every 12 hr for 6 days) produced significant decreases in the Vmax of brainstem (-32.8%) and forebrain (-31.5%) tryptophan hydroxylase when measured 12 hr after the final injection. Serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and [3H]5-HT synaptosomal uptake were decreased by a similar magnitude following chronic drug treatment. Administration of fluoxetine prior to each methamphetamine injection prevented these neurochemical changes. Neither acute nor chronic methamphetamine treatment produced any significant changes in the Km of tryptophan hydroxylase for either substrate or cofactor. Systemic tryptophan loading (50 mg/kg, i.p.) one hour prior to sacrifice in chronic methamphetamine treated rats restored brain 5-HT and 5-HIAA levels to normal. These data suggest that chronic methamphetamine treatment decreases central serotonergic neurotransmission by reducing the activity of the rate-limiting enzyme in 5-HT biosynthesis, possibly by disrupting serotonergic nerve terminals.

Animals↗
PubMed1992

Characterization of tryptophan and coenzyme luminescence in tryptophan synthase from Salmonella typhimurium.

Tryptophan synthase from Salmonella typhimurium is a bifunctional alpha 2 beta 2 complex that catalyzes the formation of L-tryptophan. We have characterized over the temperature range from 160 to 293 K the fluorescence and phosphorescence properties of the single tryptophan present at position 177 of the beta-subunit and of the pyridoxal 5'-phosphate bound through a Schiff's base in the beta-active site. The comparison between the fluorescence of the pyridoxal phosphate bound either to the protein or to valine free in solution indicates substantial protection for the coenzyme against thermal quenching and a greater intensity of the ketoenamine tautomer band. Trp-177 is highly luminescent, and its proximity to the pyridoxal moiety leads to an over 50% quenching of its fluorescence with both reduced and native coenzyme. The Trp phosphorescence spectrum possesses a narrow, well-defined, 0-0 vibrational band centered at 418.5 nm, a wavelength that indicates strong polar interactions with neighboring charges. The observation of delayed fluorescence in the native complex implies that the excited triplet state is involved in a process of triplet-singlet energy transfer to the ketoenamine tautomer. The rate of energy transfer, heterogeneous in low-temperature glasses with rate constants of 2.26 and 0.07 s-1, becomes homogeneous in fluid solutions as the coenzyme tautomer interconversion is likely faster than the phosphorescence decay. In both apo- and holo-alpha 2 beta 2, the phosphorescence from Trp-177 is long-lived even at ambient temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1988

Detection and identification of transient intermediates in the reactions of tryptophan synthase with oxindolyl-L-alanine and 2,3-dihydro-L-tryptophan. Evidence for a tetrahedral (gem-diamine) intermediate.

The reactions of 2,3-dihydro-L-tryptophan (DHT) and oxindolyl-L-alanine (OXA) with tryptophan synthase have been investigated by rapid-scanning stopped-flow (RSSF) spectroscopy and by the concentration dependence of rates measured by single-wavelength stopped-flow (SWSF) spectroscopy. The RSSF spectral changes for DHT and OXA show the disappearance of the internal aldimine (lambda max 412 nm), the formation and decay of intermediates absorbing less than or equal to 340 nm, and the appearance of the quinonoid (lambda max 492 and 480 nm, respectively). Rate constants determined by SWSF were either well resolved (i.e., k1[DHT], k-1 greater than k2, k-2 greater than k3, k-3) or indicative of a tightly coupled system (i.e., k1[OXA], k-1 greater than or equal to k2, k-2 greater than k3, k-3). The RSSF spectral changes and SWSF kinetic studies together with computer simulations of the kinetic time courses are consistent with a mechanism that includes formation of a bleached species. Detection of these shorter wavelength species in the reactions of OXA and DHT indicates that substrate analogues with tetrahedral geometry at C-3 induce new protein-substrate interactions that result in the accumulation of species not previously detected in the tryptophan synthase system. The bleached species with lambda max less than or equal to 340 nm are proposed as the gem-diamine intermediates.

Alanine↗
PubMed1976

Naturally occurring sites within the Shigella dysenteriae tryptophan operon severely limit tryptophan biosynthesis.

We investigated the structural, functional, and regulatory properties of the Shigella dysenteriae tryptophan (trp.) operon in transduction hybrids in which the cysB-trp-region of Escherichia coli is replaced by the corresponding region from S. dysenteriae. Tryptophan biosynthesis was largely blocked in the hybrids, although the order of the structural genes was identical with that of E. coli. Nutritional tests and enzyme assays revealed that the hybrids produced a defective anthranilate synthetase (ASase). Deletion mapping identified two distinct sites in trpE, each of which was partially responsible for the instability and low activity of ASase. We also discovered a pleiotropic site trpP (S) that maps outside the structural gene region and is closely linked to the S. dysenteriae trp operator. trpP (S) reduced the rate of trp messenger ribonucleic acid synthesis, and consequently trp enzyme levels, 10-fold relative to wild-type E. coli. In recombinants in which the structural genes of E coli were under the control of the S. dysenteriae promoter, enzyme levels were also reduced 10-fold. In some fast-growing revertants of the original hybrids, the rates of trp messenger ribonucleic acid synthesis and levels of tryptophan synthetase were restored to values characteristic of wild-type E.coli. Thus, the Trp auxotrophy associated with the S dysenteriae trp operon derives from the combination of a defective ASase and decreased expression of the entire operon imposed by trpP (S).

Anthranilate Phosphoribosyltransferase↗
PubMed1975

Tryptophan operon read-through. Isolation and characterization of an abnormally long tryptophan synthetase alpha subunit from a frame-shift mutant of Escherichia coli.

A new mutant strain of Escherichia coli, strain ICR-47, contains a frame-shift mutation in the trpA gene, the gene most distal to the operator in the trp operon. Mapping experiments indicate that the lesion is located at a site within 10 to 15% of the end of this gene. The mutation results in "out-of-phase" translation of the distal portion of the trp mRNA; normal translational termination signal(s) are not encountered and a trpA gene product longer than the wild type protein is produced. As with the other enzymes produced from this operon, the in vivo level of the altered protein (the alpha subunit of the tryptophan synthetase enzyme complex) is controlled by exogenous L-tryptophan. The altered alpha subunit from the strain ICR-47 has been isolated and characterized. Molecular weight estimations indicate a molecular weight of approximately 37,000, an increase beyond the wild type enzyme corresponding to an additional 50 to 70 amino acid residues. The protein has a new COOH-terminal amino acid sequence. Results of preliminary hybridization experiments suggest that the ICR-47 mRNA, which is necessarily longer than that needed to code for wild type enzyme, is not detectably different in size from wild type mRNA. The enzymatic properties of the ICR-47 alpha subunit indicates a greatly reduced ability of the mutant subunit to combine functionally with wild type beta2 subunit, the second protein component in the tryptophan synthetase enzyme complex. In contrast, only 40 to 50% of the intrinsic enzymatic activity of the alpha subunit is lost.

Amino Acids↗
PubMed1979

Influence of L-tryptophan on the activity of tryptophan oxygenase in rat liver slices.

Earlier experiments in vivo with adrenalectomized rats showed that for the induction of tryptophan oxygenase and tyrosine aminotransferase small doses of cortisone acetate and the corresponding substrate are necessary. We performed the similar experiments in vitro with liver slices from adrenalectomized rats which were pretreated with cortisone acetate in vivo. Studies with alpha-amanitine and cordycepin--given in vivo--showed, that the synthesis of m -RNA for tryptophan oxygenase after application of 1 mg/kg cortisone acetate lasted for less than 2 h. The results obtained in vitro were very similar to those reported earlier. Maximum activity is obtained in the presence of the substrate L-tryptophan. When adding other amino acids instead of the substrate no effect can be observed. The same is true also for actinomycin D. In the presence of puromycin and cycloheximide the enzyme activity decreases.

Amanitins↗
PubMed1977

Modulation of brain tryptophan hydroxylase activity by brain tryptophan content.

Although hydroxylation of tryptophan (TP) is considered to be the rate-limiting step in serotonin synthesis, the mechanism whereby tryptophan hydroxylase (TPH) participates in the regulation of serotonin synthesis is still in question. Since the brain TP concentration is probably near the Km for tryptophan hydroxylase, changes in brain TP content could affect the rate of its hydroxylation. However, it has not been established whether in vivo the activity of TPH and TP in several brain nuclei and other regions of rat brain after treatments known to lower brain TP levels. Chlorimipramine, loading with neutral amino acids and a TP-deficient diet decreased the TP content of some, but not all, brain regions studied. Whenever TP decrease withe TP injections. Several brain nuclei accumulate TP at different rates after a TP load. These data suggest possible mechanisms for regulation of serotonin synthesis in the face of fluctuating plasma levels of TP.

Amino Acids↗
PubMed1999

Specific enzymatic chlorination of tryptophan and tryptophan derivatives.

In the search for an alternative to chemical halogenation reactions using the free halogens, a novel type of halogenating enzymes was detected. In contrast to haloperoxidases, these NADH-dependent halogenases are specific. Tryptophan halogenase which catalyses the regioselective chlorination of tryptophan to 7-chlorotryptophan can also chlorinate tryptamine, tryptophol, indole-3-acetonitrile, and 3-methylindole. However, indole-3-acetonitrile is not chlorinated in the 7-position, but in positions two and three of the indole ring. Chlorination in the 3-position is obviously stereospecific. In addition to tryptophan and indole derivatives, aminophenylpyrrole is also accepted as a substrate for regioselective chlorination. Since the new NADH-dependent halogenases have a fairly broad substrate specificity and catalyse regioselective chlorination reactions they could be a good alternative to chemical halogenation.

Halogens↗
PubMed1990

Tryptophan fluorescence studies of ferredoxin:NADP reductase indicate the presence of tryptophan in or near the ferredoxin binding site.

The tryptophan fluorescence properties of the flavoprotein ferredoxin:NADP reductase have been examined. Although not sensitive to changes in pH or salt concentration, the tryptophan fluorescence is affected by the presence of substrates for the flavoprotein. While NADP addition results in a slight quenching of the fluorescence, ferredoxin decreases the fluorescence by nearly 50%, suggesting the presence of tryptophan in or near the ferredoxin binding site. Titration of this effect gives a dissociation constant for the ferredoxin: flavoprotein complex which is similar to that obtained by spectral perturbations. This approach has also been used to demonstrate that a chemically modified ferredoxin which does not produce spectral perturbations when added to flavoprotein is capable of interacting with the flavoprotein although with a higher dissociation constant than for native ferredoxin.

Binding Sites↗
PubMed1988

Decrease in plasma tryptophan after tryptophan-free amino acid mixtures in man.

Male healthy subjects, fasting 12 hours, ingested increasing amounts of a mixture containing a fixed proportion of seven essential amino acids (L-isoleucine 11.5%, L-leucine 18.0%, L-lysine 13.1%, L-methionine 18.0%, L-phenylalanine 18.0%, L-threonine 8.2%, L-valine 13.1%) and lacking tryptophan. The diets produced a rapid fall in plasma tryptophan which was proportional to the total amount of the amino acids ingested. Following the highest dose administered (36.6 g) plasma tryptophan fell to a minimum of about 35% the initial level and remained markedly reduced at 6 hours after treatment. The mechanism of this decrease and its potential clinical relevance are discussed.

Adult↗
PubMed1982

The treatment of depression in general practice: a comparison of L-tryptophan, amitriptyline, and a combination of L-tryptophan and amitriptyline with placebo.

One hundred and fifteen patients from 5 general practices participated in a 12-week, double-blind study comparing L-tryptophan, amitriptyline, L-tryptophan-amitriptyline combination and placebo in the treatment of depression. Analysis of total score on the Hamilton Depression Scale and a global rating of depression showed that all 3 active treatments were more effective than placebo. Significantly more patients were withdrawn as treatment failures in the placebo group compared with the active treatment groups. Side-effects necessitated withdrawal of more patients from the amitriptyline group than from the other active treatment groups, but this difference was not significant. Plasma amitriptyline and nortriptyline levels were similar in the amitriptyline and combined treatment groups. Standard haematological and biochemical profiles did not alter significantly in any group, but mean heart rate was significantly increased in patients receiving amitriptyline. There was no change in free or total plasma tryptophan concentration with treatment or on remission of symptoms.

Adolescent↗