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β-3-Oxindolylalanine (hydroxytryptophan). 2. Spectroscopic and chromatographic properties

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... Although 5-OH Trp has been well-characterized as it is a metabolic intermediate in the formation of serotonin, 34 it was not detected in the present study as it is not a predominant Trp oxidation product in free Trp or proteins, consistent with the recent report by Hogan et al. 22,23 NFK and Kyn oxidation products are well characterized due to their strong absorbance in the visible region and distinct mass differences (þ32 Da and þ4 Da, respectively), 12,42 but the oxidation product, 2OH-Trp, is not well characterized. Notably, these Trp oxidation products in proteins exhibit weak fluorescence emission spectra on excitation at 295 nm, and each species has a unique absorbance profile and Raman markers. ...
Article
Tryptophan (Trp) oxidation in proteins leads to a number of events, including changes in color, higher order structure (HOS), and biological activity. We describe here a number of new findings through a comprehensive characterization of 6 monoclonal antibodies (mAbs) following selective oxidation of Trp residues by 2,2’-azobis(2-amidinopropane) dihydrochloride. Fluorescence spectroscopy, in combination with second derivative analysis, demonstrates that the loss of Trp fluorescence intensity is a sensitive indicator of Trp oxidation in mAbs. Size-exclusion chromatography with UV and intrinsic Trp fluorescence detection was demonstrated to be a useful method to monitor Trp oxidation levels in mAbs. Furthermore, the Trp oxidation levels measured by size-exclusion chromatography with UV and intrinsic Trp fluorescence detection were found to be in agreement with the values obtained from tryptic peptide mapping by liquid chromatography with mass spectrometric detection and correlate with the total solvent accessible surface area of the exposed Trp residues from in silico modeling. Finally, near-UV circular dichroism and Raman spectroscopy were used to evaluate the impact of Trp oxidation on HOS and identify specific oxidation products, respectively. This work demonstrates that protein HOS is altered on Trp oxidation in mAbs and multiple spectroscopic markers can be used to monitor the molecule-dependent Trp oxidation behavior.
... In later studies, TH. WIELAND and SCHMIDT (74) demonstrated the peculiar nature of the linkage between cysteine and tryptophan, previously suggested by NEUBERGER et al. (7) on the basis of spectroscopic observations. The oxindolylalanine building block, when isolated, exhibits maximum absorption at 250 mil (indicating a N-acylaniline rather than an indole spectrum), whereas in phalloidin the greater wave-length maximum (292 mp) points to an indole conjugation. ...
Fatal mushroom poisoning is almost exclusively attributable to members of the genus Amanita. In the United States, it is Amanita verna, the so called “destroying angel”, which along with another poisonous species, A. tenuifolia, appears to play the major part in lethal mushroom poisoning (1, 2). Quite recently we were able to demonstrate the presence of the two main amanita toxins in a European sample of A. verna (73). Besides these mushrooms some relatively rare Galerina species also contain the amanita toxins (42). In Central Europe the predominant culprit is the greenish Amanita phalloides (Fig. 1). This mushroom, also known as the “deadly agaric”, is frequently confused with the delicious field mushroom Agaricus campestris or with the yellow Amanita mappa (citrina), which contains no toxic peptides, but the relatively untoxic bufotenine (5-hydroxy-N-dimethyl-tryptamine) (67, 43), a base occurring in toads and recently isolated also from different plants, among them Piptadenia peregrina (12), P. macrocarpa and P. excelsa (20), Desmodium pulchellum (19) or from Epena, a drug from a woody South American Leguminosa (28).
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The stability of Trp in pure solutions and in parenteral AA formulations was evaluated with regard to typically used manufacturing processes, storage conditions and primary packaging. Therefore, thorough stability studies on Trp solutions were conducted beforehand. The applied stressing method, i.e. steam sterilization by autoclave, are chemically seen relatively mild but showed to be efficient to induce Trp degradation in the presence of oxygen. Subsequent identification, separation and characterization were challenging due to similar substance properties, numerous stereoisomers and pairs of diastereomers found amongst them. However, the identified o-aminoacetophenone compounds, Kyn and NFK, are associated with photo reactivity and have photo-oxidizing properties. Thus, best possible protection from UV-light, together with strict oxygen expulsion, are the most important criteria to impede Trp degradation after autoclaving. The identification of Trp degradation products was assisted by the compilation of a substance library, which included manifold reported and chemically plausible Trp degradation substances. The substances were classified for priority and their early or late-stage occurrence. The large number of possible substances and stereoisomers was narrowed down with the information retrieved from LC-UV/MS experiments. However, final identification was achieved by the synthesis of proposed substances as references. The following eight substances were characterized as Trp degradation substances: Kyn, NFK and three pairs of diastereomers R,R/R,S DiOia, R,R/R,S Oia and cis/trans PIC. Fig. 33 shows the proposed degradation pathway and demonstrates the close chemical relationship, which may be an explanation for the conversion of some substances into each other during the storage period. The proposed pathway brings together the results of different Trp stability and stressing studies, respectively [89, 94, 97, 98, 103, 133]. To our knowledge, the simultaneous formation of the identified degradation substances has not been reported before and especially not under the stressing conditions applied. The application of a traditional RP-HPLC method was compared to two developed IP-HPLC methods and a RP-HPLC methods using a modified perfluorinated column. Orthogonal analyses methods and especially the combination of UV and MS detection are necessary in order to indicate potentially undetected degradation substances. Main evaluation criteria were the separation performance, analyses time, reproducibility and feasibility. The best results upon assessment of all Trp degradation products, in both; pure Trp solutions and pharmaceutical formulations, were obtained by a traditional RP-HPLC. The optimized method was validated according to ICH guidelines Q2(R1) and meets the criteria of a stability-indicating HPLC-UV method. The validated method has a sufficient separation performance with an adequate selectivity indicating the Trp degradation substances next to each other and next to other AAs in finished pharmaceutical formulations. The detailed knowledge of Trp degradation and the method presented may be transferred practically to the pharmaceutical industry processing Trp-containing products. In general, the findings might contribute to the quality management of such pharmaceutical products during manufacturing and storage. Additionally, the study results provide basic information for the establishment of an impurity consideration following the ICH guidelines Q3B (R2) (impurities in new drug products) for products containing Trp. However, further development of the method applying more sophisticated detectors or more potent HPLC techniques like e.g. UHPLC and the implication of more sensitive (MS) detectors like ToF-MS would be advantageous with regard to economic and practical aspects.
Article
The chapter discusses the metabolism of phenylalanine, tyrosine, and tryptophan. Phenylalanine acid tryptophan is “essential” amino acids for higher organisms— that is, they cannot be synthesized by the organism and must be supplied in the diet. Tyrosine, formed from phenylalanine acid is not essential if the phenylalanine intake is adequate. The chapter presents biosynthesis, which is confined to lower organisms (bacteria, fungi, plants, etc.). Shikimic acid is a common precursor of the aromatic amino acids and of the bacterial growth factors, p-amino- and p-hydroxybenzoic acids. Phenylalanine and tyrosine are metabolized in higher organisms by two routes, which are quantitatively less important but physiologically of the highest importance. The first leads to the adrenal hormones adrenaline (epinephrine) and nonadrenaline (norepinephrine); this pathway also leads to melanin. The second leads to the thyroid hormones thyroxine and triiodothyronine, the synthesis and breakdown of which are also discussed. Tryptophan is metabolized in a wide range of organisms by a pathway involving: an unknown intermediate, formylkynurenine, kynurenine, hydroxykynurenine (or its phosphate), hydroxyanthranilic acid (or its phosphate), two unknown intermediates, and nicotinic acid. The relation of other vitamins to the pathway, side reactions giving such substances as anthranilic acid, kynurenic acid, and xanthurenic acid and the further degradation of nicotinic acid and its relation to the pyridine nueleotides are also considered. Tryptophan also gives rise to the important plant hormone, indoleacetic acid, and micro-organisms and especially plants metabolize the aromatic amino acids to a wide range of natural products, for example, certain antibiotics, alkaloids, flavonoids, and possibly lignin.
Article
This chapter discusses naturally occurring peptides, which allows several generalizations concerning their importance as distinct chemical entities. Certain physiologically active naturally occurring peptides seem to be linked to the much larger protein molecules with respect to their structure and physiological activity. The distinction is based largely on the fact that naturally occurring peptides are composed of amino acids with uncommon configurations and structures, and of linkages other than the classical peptide bond. The uncommon structures exist only rarely in proteins and this would be exactly why one can use them to differentiate the naturally occurring peptides from protein fragments. One group, containing heteromeric peptides, is characterized on the basis of a common structure and an identical amino acid composition, differing from one another by the nature of the heteromeric group. Such is the case of the penicillins. Another group also has a given identical structure, but each member of the group has a different amino acid composition. All the members of such families possess the same number of amino acids, however, are of a different nature. All the members of another group possess the same heteromeric groupings and uncommon amino acids, but they differ by the number and nature of other amino acids. The characteristic biological actions of the naturally occurring peptides are because of their uncommon structures and compositions. The biological activity is related to the structure. The existence of naturally occurring peptides show that nature utilizes amino acids to build proteins and peptides.
Article
The results of 50 years of effort in the chemistry of Amanita toxins are reviewed. The phallotoxins, fast acting components, but not responsible for fatal intoxications after ingestion, are bicyclic heptapeptides. They combine with F-actin, stabilizing this protein against several destabilizing influences. The virotoxins likewise fast acting are monocyclic heptapeptides. The amatoxins which are the real toxins lead to death within several days by inhibiting the enzymatic synthesis of m-RNA. They are bicyclic octapeptides. The structures of all of these compounds are described, as well as conformations, chemical reactions and modification, syntheses and correlations between structures and biological activities.
Article
— Seven chromatographically separable products were shown to be formed when an aqueous solution of tryptophan was exposed to the light of a 100-W bulb at pH 9 in the presence of methylene blue and oxygen. Some of these products were detected, though in much smaller quantities, even when tryptophan was irradiated in the absence of methylene blue and/or oxygen. Contrary to reports in the literature, none of the common derivatives of tryptophan, such as tryptamine, indole acetic acid, indole aldehyde, anthranilic acid or kynurenine, were detected on irradiation of the amino acid by visible light. Such irradiation of tryptamine and indole acetic acid gave 1–2 components which were chromatographically identical with those obtained from tryptophan; irradiation of indole aldehyde gave no detectable breakdown products. Exposure of tryptophan to ultraviolet light or when treated with hydrogen peroxide did not result in the formation of any of the products obtained with visible light. The results presented here suggest that during exposure of tryptophan to visible light, the indole ring is first oxygenated resulting in the formation of dioxindole derivatives. One of the products of irradiation of tryptophan with visible light was tentatively identified as dioxin-dolylalanine.
Lysozyme was irradiated in dilute aqueous solutions with 60Co γ-rays. Variation of pH, the presence or absence of oxygen and nitrous oxide and other additives has made it possible to investigate the separate roles of hydroxyl radicals, solvated electrons, and hydrogen atoms as inactivating species. Hydrogen atoms inactivate the enzyme with an effectiveness that increases at low pH values; electrons are not particularly effective. The hydroxyl radical is the species responsible for about 90 per cent of the inactivation at intermediate pH. Inactivation measurements on solutions irradiated at different pH values show that the sensitivity to inactivation by hydroxyl radicals and hydrogen atoms depends on the configuration of the protein. The mechanism of the reaction with the hydroxyl radical in the presence and absence of oxygen has been studied by u.v.-absorption changes and probably involves oxindolylalamine or kynurenine structures. Changes in aggregation and molecular conformation have been investigated by gel filtration and optical rotatory dispersion. The evidence suggests that reaction of the hydroxyl radical with tryptophan residues is largely responsible for the radiation-induced inactivation.
Article
Under hydrolytic conditions using 6 M HCl, tryptophan reacted separately with dithiodiglycolic acid and cystine to give beta-3-oxindolylalanine (beta-[3-(2-indolinone)]alanine) as the main product. A compound, which eluted in the amino acid analyzer at the same position as beta-3-oxindolylalanine, was found in the acid hydrolyzate of lysozyme. The identicalness of these two compounds was established by comparison of their ultraviolet absorption spectra, elution positions on ion exchange chromatograms, etc. The "acid degradation product of tryptophan", which is known to be produced upon acid hydrolysis of tryptophan-containing proteins, must also be the same compound.
Article
1.1. Changes in the absorption spectrum during the oxidation of IAA by the Omphalia enzyme or horse-radish peroxidase indicate the formation and disappearance of an intermediate. The reaction takes place in two spectrophotometrically distinguishable steps, the first of which can be followed at 261 mμ and the second at 272 mμ (at pH 3.7). The first step converts IAA to the intermediate, and the second transforms the intermediate to the final products.2.2. Bisulfite (3 × 10−3M) reacts with the intermediate but not with IAA or the final products, and so confirms the chemical individuality of the intermediate and provides a means of measuring its concentration.3.3. The first step is catalyzed by the enzyme, while the second one is spontaneous and acid-catalyzed. The first step consumes one molecule of oxygen per molecule of IAA; the second step does not involve either oxygen or H2O2.4.4. With labeled IAA it is shown that the intermediate is a neutral substance, and deduced that carbon dioxide is formed in the first step.5.5. The final product appears to consist of at least two, and possibly more, substances as soon as it is formed, so that the second step involves the decomposition of the intermediate along more than one pathway.6.6. The spectrum of the intermediate resembles spectra of indole derivatives, even though that of the final product does not. The most likely structure for the intermediate seems to be a skatole nucleus oxidized in the 1- and 2-position or both.
Article
Tryptophan is readily oxidized to oxindolylalanine (2-hydroxytryptophan) in good yield on treatment in acetic acid solution with a mixture of dimethyl sulfoxide (DMSO) and concentrated aqueous HCl at room temperature. Other sulfoxides can be used in combination with HCl; for example, methionine sulfoxide reacts with an equimolar amount of tryptophan to give high yields of methionine and oxindolylalanine. Methionine and cysteine are quantitatively oxidized by DMSO/HCl to methionine sulfoxide and cystine, respectively. The tryptophan containing peptides LRF (luteinizing hormone-releasing factor), somatostatin, valine-gramicidin A and ACTH1–24were each treated with the DMSO/HCl reagent in acetic acid solution and the corresponding oxindolylalanine-derivatives isolated in over 90% yield after chromatography. The identity and purity of the derivatives were established on the basis of ultraviolet spectral characteristics and quantitative amino acid analysis of the oxindolylalanine content of acid hydrolyzates of the oxidized peptides with 3N-p-toluenesulfonic acid at 110° for 24 h. The results indicate that modification of tryptophan peptides with DMSO/HCl provides a useful procedure, which seems superior to previously used reagents. In addition, the method could be well applied to other indoles of biological and pharmacological interest.
Article
A partial formulation of the characteristic colouring matter of suint from normal sheep is presented. The fundamental molecular unit is methyl 10– (2,5–dihydroxyphenyl)–decanoic acid, and this is associated, usually nonstoichiometrically, with a nitrogenous β-diketone.
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The heme enzyme indoleamine 2,3-dioxygenase (IDO) is a key regulator of immune responses through catalyzing l-tryptophan (l-Trp) oxidation. Here, we show that hydrogen peroxide (H2O2) activates the peroxidase function of IDO to induce protein oxidation and inhibit dioxygenase activity. Exposure of IDO-expressing cells or recombinant human IDO (rIDO) to H2O2 inhibited dioxygenase activity in a manner abrogated by l-Trp. Dioxygenase inhibition correlated with IDO-catalyzed H2O2 consumption, compound I-mediated formation of protein-centered radicals, altered protein secondary structure, and opening of the distal heme pocket to promote nonproductive substrate binding; these changes were inhibited by l-Trp, the heme ligand cyanide, or free radical scavengers. Protection by l-Trp coincided with its oxidation into oxindolylalanine and kynurenine and the formation of a compound II-type ferryl-oxo heme. Physiological peroxidase substrates, ascorbate or tyrosine, enhanced rIDO-mediated H2O2 consumption and attenuated H2O2-induced protein oxidation and dioxygenase inhibition. In the presence of H2O2, rIDO catalytically consumed nitric oxide (NO) and utilized nitrite to promote 3-nitrotyrosine formation on IDO. The promotion of H2O2 consumption by peroxidase substrates, NO consumption, and IDO nitration was inhibited by l-Trp. This study identifies IDO as a heme peroxidase that, in the absence of substrates, self-inactivates dioxygenase activity via compound I-initiated protein oxidation. l-Trp protects against dioxygenase inactivation by reacting with compound I and retarding compound II reduction to suppress peroxidase turnover. Peroxidase-mediated dioxygenase inactivation, NO consumption, or protein nitration may modulate the biological actions of IDO expressed in inflammatory tissues where the levels of H2O2 and NO are elevated and l-Trp is low. Background: Certain heme proteins exhibit a pseudo-peroxidase activity that alters their function. Results: H2O2 engages the peroxidase activity of indoleamine 2,3-dioxygenase (IDO) to oxidatively inactivate its dioxygenase activity, consume nitric oxide, and promote IDO protein nitration. Conclusion: IDO is a catalyst of physiological peroxidase reactions. Significance: IDO peroxidase activity has novel implications for the control and biological actions of this important immune regulatory enzyme.
Article
Das Calebassen-Alkaloid C-Fluorocurarin (C-Curarin III), welches auch als Spaltprodukt des C-Curarins I und des C-Calebassins bekannt ist, wurde in bezug auf seine Konstitution eingehend untersucht. Es erwies sich als ein α,β-ungesättigter Aldehyd, dessen Aldehydgruppe an ein α-Methylen-indolin-System angeschlossen ist und mit diesem die chromophore Gruppe bildet. Eine für C-Fluorocurarin wahrscheinliche Konstitutionsformel wird vorgeschlagen und diskutiert.
Article
Es wird über Methoden für den Nachweis und die Bestimmung kleiner Mengen verschiedener Abbauprodukte des Tryptophans — auch in biologischen Flüssigkeiten —, die von zahlreichen Autoren ausgearbeitet wurden, berichtet. Hierbei handelt es sich um Kynurenin, 3-Hydroxykynurenin, Anthranilsäure und 3-Hydroxyanthranilsäure, Kynuren- und Xanthurensäure. Um das Interesse an jenen Forschungen verständlich zu machen, wird kurz hervorgehoben, daß sich die Anwendung dieser analytischen Methoden nicht auf die biologische Forschung beschränkt, sondern sich auf die Physiopathologie des Menschen ausdehnen läßt.
1.1. The near-ultraviolet circular dichroism (CD) spectra of β-3-oxindolyl-l-alanine (β-[3-(2-indolinone)]-l-alanine) and ethyl ester have been studied. The longest wavelength CD band is centered at 280–285 nm. Another band occurs at 245–254 nm. In the case of β-3-oxindolyl-l-alanine, the intensities of these CD bands are affected by pH; both bands are positive at pH 1.5 and negative at pH 7. ethyl ester has negative CD bands in a variety of solvents (ΔεM about −3 at 252 nm and about −0.4 M−1 · cm−1 at 283 nm).2.2. The CD spectra anticipated from tryptophan oxidized in a protein are discussed. Depending upon which tautomeric form of oxindole is produced, the modified tryptophanyl side chain may exhibit one of several different types of CD spectra. In all cases, the modified side chain may have CD bands that overlap the naturally occurring tryptophanyl CD bands.
Article
During metamorphosis of Protophormia terrae-novae, tryptophan is degraded quantitatively to kynurenine, 3-hydroxykynurenine, and xanthommatin; kynurenic and xanthurenic acids are detected in trace amounts, while anthranilic and 3-hydroxyanthranilic acids are apparently not formed. Tryptophan is taken up rapidly by growing tissues and by the excretory system. The enzymes of tryptophan catabolism were found to follow individual activity patterns during development: tryptophan oxygenase displays a U-curve, kynurenine formamidase decreases steadily from the larval to adult stages, while kynurenine hydroxylase is maximal prior to pupation.
Article
Albert Neuberger was born in 1908 in the small Franconian town of Hassfurt, which is in the north of Bavaria. At the time of Albert's birth, the Kingdom of Bavaria was a semiautonomous state of the German Empire.
Chapter
The study of peptides in plants has been dominated by two aims. Most of the work described here has been carried out in order to identify some “active principle”, which has turned out to contain peptide bonds. Such “principles” may be active towards bacteria (e.g. gramicidin, penicillin, etc.), plants (e.g. lycomarasmin) or animals (e.g. the ergot alkaloids). The primary interest in much of this work has been to determine the structure of these physiologically active peptides; it is not generally known why they are active, nor the part they play in the metabolism of the organisms whence they originated. Chemically, these peptides are interesting in the variety of structures displayed and in the methods used to purify them and determine their structure; the use of these methods is a guide to the methods likely to be of promise in the purification and structure determination of proteins. Biologically, too, these physiologically active peptides serve as a reminder of the many possible complexities latent in the protein molecule. The second aim in the study of peptides is a more general one. Living cells commonly contain a score or so of amino-acids and many proteins, and the proteins themselves usually have at least 100 amino-acid residues in their molecules. Whether molecules of intermediate size are present (and if so, the part they play in protein metabolism) is an important, but largely unanswered, question. This section is written from the point of view that the main interest in the “active principle” type of work lies in the structure of the products, whereas the main interest at the moment in the second type of work lies in the analytical techniques. One of the most frequently used techniques is paper chromatography; its application to the study of the nitrogenous constituents of plants is described in a review by Steward and Thomson (1950).
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