This Article Full Text (PDF) Other Versions of this Article: JB.01192-06v1 189/5/1664    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Cámara, B. Articles by Pieper, D. H. Search for Related Content PubMed PubMed Citation Articles by Cámara, B. Articles by Pieper, D. H.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.01192-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

A gene cluster involved in degradation of substituted salicylates via ortho-cleavage in Pseudomonas sp. strain MT1 encodes enzymes specifically adapted for transformation of 4-methylcatechol and 3-methylmuconate

Division of Microbiology, HZI - Helmholtz Zentrum für Infektionsforschung, Inhoffenstrasse 7, D-38124 Braunschweig, Germany

^* To whom correspondence should be addressed. Email: dpi{at}helmholtz-hzi.de.

	Abstract

Pseudomonas sp. strain MT1 has recently been described to degrade 4- and 5-chlorosalicylate by a pathway assumed to consist of a patchwork of reactions comprising enzymes of the 3-oxoadipate pathway. Genes encoding the initial steps in the degradation of salicylate and substituted derivatives were now localized and sequenced. One of the characterized gene clusters (sal) showed a novel gene arrangement with salA encoding a salicylate 1-hydroxylase being clustered with salCD genes encoding muconate cycloisomerase and catechol 1,2-dioxygenase, respectively, and was expressed during growth on salicylate and chlorosalicylate. A second gene cluster (cat), exhibiting the typical catRBCA arrangement of genes of the catechol branch of the 3-oxoadipate pathway in Pseudomonas strains, was expressed during growth on salicylate. Despite their high sequence similarity with isoenzymes encoded by the cat gene cluster, catechol 1,2-dioxygenase and muconate cycloisomerase encoded by the sal cluster showed unusual kinetic properties. Enzymes were adapted for turnover of 4-chlorocatechol and 3-chloromuconate; however, 4-methylcatechol and 3-methylmuconate were identified as the preferred substrates. Investigation of the substrate spectrum identified 4- and 5-methylsalicylate as growth substrates, which were effectively converted by enzymes of the sal cluster into 4-methylmuconolactone, followed by an isomerization to 3-methylmuconolactone. The function of the sal gene cluster is therefore to channel both chlorosubstituted and methylsubstituted salicylates into a catechol ortho-cleavage pathway followed by dismantling of the formed substituted muconolactones through specific pathways.