Pseudomonas, tryptophan metabolism

Rosenfeld H, Feigelson P (1969) Synergistic and product induction of the enzymes of tryptophan metabolism in Pseudomonas acidovorans. J Bacteriol 97(2) 697-704 Rosso A, Ferrarotti S, Miranda MV et al. (2005) Rapid affinity purification processes for cyclodextrin glycosyltransferase from Bacillus circulans. Biotechnol Lett 27(16) 171-1175 Rowan AD, Butte DJ, Barrett AJ (1990) The cysteine proteinases of the pineapple plant. Biochem J 266 869-875... 

Pyrrolnitrin (137) and 3-chloroindole (138) are two products of tryptophan metabolism in Pseudomonas pyrrocinia and Pseudomonas aureofaciens °. The occurrence of phenylpyrrole compounds in nature is rare and it has been suggested that the antifungal compound pyrrolnitrin (137) is produced from tryptophan in a reaction initiated by a chloroperoxidase system Figure 4.21). 

The outcome of the different lines of investigation is that a number of pathways of tryptophan metabolism have been established. In the vertebrate organism the two well-known pathways are the kynurenine-hydroxyanthranilic acid and the serotonin pathways. Studies with Pseudomonas bacteria led Stanier and Hayaishi (876) to propose two pathways for the dissimilation of the products of tryptophan metabolism starting at the level of kynurenine. One of these is through anthranilic acid and catechol, referred to as the aromatic pathway, and the other through kynurenic acid, named the quinoline pathway. 

Lubbe C, K-H van Pee, O Salcher, F Lingens (1983) The metabolism of tryptophan and 7-chlorotryptophan in Pseudomonas pyrrocinia and Pseudomonas aureofaciens. Zphysiol Chem 364 447-453. 

Hydroxytryptophan was not metabolized by a tryptophan-adapted strain of Pseudomonas (217) and was not attacked by the tryptophan peroxidase-oxidase system (217, 884). The enteramine and kynurenine pathways are quite distinct, as is supported by the facts that synthetic 5-hydroxykynurenine (124, 574), the expected product of tryptophan peroxidase-oxidase action, does not act as an ommochrome precursor in insects or as a nicotinic acid precursor in Neurospora (124). 

Racemic tryptophan similarly gave 4,/-12, the methyl ester and 2-methyl derivatives gave the corresponding quinazolines, but the JV-acetyl derivative failed to yield a quinazoline and gave AT-acetyl-iV -formylkynurenine. Clearly the pyrrole ring was cleaved, and then reaction with ammonia followed by ring closure, gave the quinazoline. This is probably how the metabolism of tryptophan takes place in the quinazoline pathway in Pseudomonas (see Section VIII). 

Hamill, R. L., Elander, R. P., Mabe, J. A., and Gorman, M. (1970) Metabolism of tryptophan by Pseudomonas aureofaciens III. Production of substituted pyrrolnitrins from tryptophan analogues. Appl Microbiol 19,721—725. 

The oxidation of tryptophol to indoleacetaldehyde is not necessarily its only pathway of metabolism. The microorganism Pseudomonas fluorescens. for example, contains a tryptophan side-chain oxidase . This oxidase, at least in vitro, attacks a variety of substrates including tryptophol, to form indole-3-glycol and indole-3-ketol [Fig. 2 23] ... 

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. 

Lively, D., M. Gorman, M. Haney, and J. Mabe Metabolism of tryptophans by Pseudomonas auveofaciens. I. Biosynthesis of pyrrolnitrin. Sixth Interscience Conf. on Antimicrobial Agents and Chemotherapy, Philadelphia 1966. Abstracts p. 26. 

Pyrocatechase is an enzyme widely distributed among bacteria. It catalyzes an oxidation of o-dihydroxybenzene, and is named according to the traditional name of the substrate, pyrocatechol. Pyrocatechol, more commonly known by the abbreviated designation catechol, is an intermediate in the metabolism of many aromatic compounds, including mandelic acid, nitrobenzoic acid, anthranilic acid, and other compounds that may be converted to salicylic acid. Benzoic acid and phenol are also precursors of catechol. The best-studied enzyme is that obtained from a strain of Pseudomonas that can use tryptophan as a carbon source. The enzyme is formed adaptively when tryptophan, catechol, or any intermediate between the amino acid and catechol (Fig. 4) is used as a substrate for the cells (Suda et al., 1950). 

A third pathway of protocatechuic acid metabolism occurs in a Rhodo-pseudomonas. Proctor and Scher (1960) have reported that this organism forms protocatechuate from benzoate, then decarboxylates the product to catechol. (This is the second example of a nonoxidative aromatic decarboxylase.) Subsequent metabolism of catechol yields a keto acid not yet identified, but possibly that produced in other catechol-utilizing systems described below. A unique feature of the Rhodopseudomonas system is its reported dependence on hydrogen peroxide for the oxidation of catechol. It will be of interest to learn whether peroxide is consumed stoichiometrically in the reaction, or whether it is an activator, as has been found for tryptophan pyrrolase. 

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