Properties of the trihydroxytoluene oxygenase from Burkholderia cepacia R34: an extradiol dioxygenase from the 2,4-dinitrotoluene pathway.

Johnson, G R and Jain, R K and Spain, J C (2000) Properties of the trihydroxytoluene oxygenase from Burkholderia cepacia R34: an extradiol dioxygenase from the 2,4-dinitrotoluene pathway. Archives of microbiology, 173 (2). pp. 86-90. ISSN 0302-8933

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Abstract

Burkholderia cepacia R34 mineralizes 2,4-dinitrotoluene via an oxidative pathway. The initial steps in the degradative pathway lead to formation of 2,4,5-trihydroxytoluene, which serves as the substrate for the ring cleavage dioxygenase. The trihydroxylated substrate differs from the usual substituted catechols found in pathways for aromatic compound degradation. To determine whether the characteristics of the trihydroxytoluene oxygenase reflect the unusual ring cleavage substrate of the 2,4-dinitrotoluene pathway, the gene encoding trihydroxytoluene oxygenase (dntD) was cloned and sequenced, and ring cleavage activity determined from recombinant bacteria carrying the cloned gene. The findings were compared to the trihydroxytoluene oxygenase from Burkholderia sp. strain DNT and to other previously described ring cleavage dioxygenases. The comparison revealed that only 60% identity was shared by the two trihydroxytoluene oxygenases, but the amino acid residues involved in cofactor binding, catalysis, and protein folding were conserved in the DntD sequence. The enzyme catalyzed meta-fission of trihydroxytoluene as well as the substrate analogues 1,2,4-benzenetriol, catechol, 3-methylcatechol, 4-methylcatechol, 3-chlorocatechol, 4-chlorocatechol and 2,3-dihydroxybiphenyl. However, results from enzyme assays indicated a strong preference for trihydroxytoluene, implying that it was the native substrate for the enzyme. The apparent enzyme specificity, its similarity to the trihydroxytoluene oxygenase from Burkholderia sp. strain DNT, and the distant genetic relationship to other ring cleavage enzymes suggest that dntD evolved expressly to carry out trihydroxytoluene transformation.

Item Type:	Article
Additional Information:	Copyright of this article belongs to Springer Science.
Subjects:	Q Science > QR Microbiology
Depositing User:	Dr. K.P.S.Sengar
Date Deposited:	02 Feb 2012 05:03
Last Modified:	02 Feb 2012 05:03
URI:	http://crdd.osdd.net/open/id/eprint/835

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