Tryptophan oxidized

Bihel, S., Birlouez-Aragon, I. 1998. Inhibition of tryptophan oxidation in the presence of iron-vitamin C by bovine lactoferrin. Int. Dairy J. 8, 637-641. 

Table III). Atomic absorption analysis shows that the copper is still present in the enzyme. These two facts coupled with the 600-nm region intensity increase might be interpreted to suggest that a stereochemical distortion accompanies tryptophan oxidation in galactose oxidase. For example, a saddling of the planar environment would be expected to lower the reduction potential of the Cu(II)-Cu(I) couple. 

The other amino acid reacting with HOC1 is tyrosine. At pH ranging from 3.5 to 6.0, HOC1 reacts with A-acetyltyrosine to produce S -chloro derivative (Fig. 8). If the HOCl/N-acetyltyrosine molar ratio exceeds 10, 3/5/-dichlorotyrosine formation is observed. The chlorotyrosine formation is slow compared to chloramine formation or tryptophan oxidation reaction rate. The optimal conditions for tyrosine... 

A number of inborn errors of metabolism of the tryptophan oxidative pathway (see Figure 8.4) have been reported, aU of which result in the development of pellagra that responds to high doses of niacin. These conditions include vitamin Be-responsive xanthurenic aciduria, caused by a defect of kynureni-nase (Section 9.4.3) hydroxykynureninuria, apparentiy caused by a defect of kynureninase tryptophanuria, apparentiy caused by tryptophan dioxygenase deficiency a hereditary pellagra-like condition, apparentiy caused by an increase in activity of picoUnate carboxylase and Hartnup disease. 

Fig. 27. Change in activity of chymotrypsin as a function of tryptophan oxidation. (A) Treatment with NBS (B) treatment with NBA. From Viswanatha and Lawson (1961).

Tryptophan oxidizes primarily via reactive oxygen species, although it may occur as a result of photooxidation in the presence of dyes. Trp and Met are the only amino acids that are capable of being oxidized below pH 4. The primary oxidation products of Trp... 

Steinhart, H. and Kirchgessner, M., Toxicity of tryptophan oxidation products in chickens, Z. Tierphysiol. Tierernahr. Futtermittelkd., 40, 332, 1978. 

Palleroni, N.J. and R.Y. Stanier. 1964. Regulatory mechanisms governing synthesis of the enzymes for tryptophan oxidation by Pseudomonas fluorescens. J. Gen. Microbiol. 35 319-334. 

The heme dioxygenase enzymes involved in tryptophan oxidation catalyse the first and rate-limiting step in the kynurenine pathway—the 02-dependent oxidation of 1-tryptophan to AT -formylkynurenine. In the past 10 years, there have been substantial new developments, including new structural information, bacterial expression systems for a number of dioxygenases, contributions from computational chemistry, and emerging... 

Search restrictions Tryptic peptides with variable methionine, histidine, tryptophan oxidation One miscleavage Peptide tolerance 50 ppm, peptide charge + 1 MS/MS tolerance 0.7 Da ... 

Besides the peroxidases already mentioned, similar enzymes have been found in various tissues where they may perform special functions. One such function may be the formation of thyroxine. A special peroxidase will be discussed in connection with tryptophan oxidation. 

The content of the tryptophan-oxidizing enzyme system present in liver commonly is low. It can be increased as much as tenfold through the prior feeding of tryptophan by a mechanism resembling that of enzyme adaptation observed in microorganisms. A much smaller response (twofold) is obtained with certain other substances not substrates of the enzyme system, e.g., epinephrine and histamine. This latter group of compounds has no effect in adrenalectomized animals, and thus, it appears, the increase is caused through a stimulation by the pituitary-adrenal system. ... 

When synthesis of this compound was accomplished, > experiments with it made it clear that it is not a normal tryptophan metabolite. The metabolism of oxindolylalanine was found to be quite different from that of tryptophan or kynurenine in rat liver slices, or in the intact animal. The paper chromatographs of the urines from normal and pyridoxine-deficient rats fed oxindolylalanine were quite different from those obtained when tryptophan was fed. Furthermore, the tryptophan peroxidase-oxidase enzyme system does not act on this compound, nor was it metabolized by the bacillus. Pseudomonas fluorescens, which had been adapted to tryptophan or kynurenine. The identity of the first intermediate of tryptophan oxidation, therefore, is still unknown. 

The main products of tryptophan oxidation with singlet oxygen are a dioxethane derivative, formed via 1,4-cycloaddition and a hydroperoxide at C-3. Subsequent decomposition of these intermediates yields N-formylkynurenine, whereas their ring closure leads to cis- and trans-isomers of 3a-hydroxypyrroloindoles, that is, 3a-hydroxy-l,2,3,3,8,8a-hexahydropyrrolo[2,3-fo]indole-2-carboxylic acids and 3a,8a-dihydroxypyrroloindoles. The simplified reaction sequences are given in Figure 2.38. 

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