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Characterization of the genes encoding the 3-carboxy-cis,cis-muconate-lactonizing enzymes from the 4-sulfocatechol degradative pathways of Hydrogenophaga intermedia S1 and Agrobacterium radiobacter S2

Tamara Basta

Matthias Contzen

Institut für Mikrobiologie, Universität Stuttgart, Allmandring 31, D-70569 Stuttgart, Germany

Correspondence
Andreas Stolz
Andreas.Stolz{at}imb.Uni-Stuttgart.de

Hydrogenophaga intermedia strain S1 and Agrobacterium radiobacter strain S2 form a mixed bacterial culture which degrades sulfanilate (4-aminobenzenesulfonate) by a novel variation of the -ketoadipate pathway via 4-sulfocatechol and 3-sulfomuconate. It was previously proposed that the further metabolism of 3-sulfomuconate is catalysed by modified 3-carboxy-cis,cis-muconate-lactonizing enzymes (CMLEs) and that these ‘type 2’ enzymes were different from the conventional CMLEs (‘type 1’) from the protocatechuate pathway in their ability to convert 3-sulfomuconate in addition to 3-carboxy-cis,cis-muconate. In the present study the genes for two CMLEs (pcaB2S1 and pcaB2S2) were cloned from H. intermedia S1 and A. radiobacter S2, respectively. In both strains, these genes were located close to the previously identified genes encoding the 4-sulfocatechol-converting enzymes. The gene products of pcaB2S1 and pcaB2S2 were therefore tentatively identified as type 2 enzymes involved in the metabolism of 3-sulfomuconate. The genes were functionally expressed and the gene products were shown to convert 3-carboxy-cis,cis-muconate and 3-sulfomuconate. 4-Carboxymethylene-4-sulfo-but-2-en-olide (4-sulfomuconolactone) was identified by HPLC-MS as the product, which was enzymically formed from 3-sulfomuconate. His-tagged variants of both CMLEs were purified and compared with the CMLE from the protocatechuate pathway of Pseudomonas putida PRS2000 for the conversion of 3-carboxy-cis,cis-muconate and 3-sulfomuconate. The CMLEs from the 4-sulfocatechol pathway converted 3-sulfomuconate with considerably higher activities than 3-carboxy-cis,cis-muconate. Also the CMLE from P. putida converted 3-sulfomuconate, but this enzyme demonstrated a clear preference for 3-carboxy-cis,cis-muconate as substrate. Thus it was demonstrated that in the 4-sulfocatechol pathway, distinct CMLEs are formed, which are specifically adapted for the preferred conversion of sulfonated substrates.

The GenBank/EMBL/DDBJ accession numbers for the pcaB2S2 and pcaB2S1 sequences reported in this paper are AY769867 and AY769868, respectively.

Present address: Institut Pasteur, 25 Rue du Dr Roux, F-75015 Paris, France.

Present address: Chemisches und Veterinäruntersuchungsamt Stuttgart, Schaflandstr. 3/2, D-70736 Fellbach, Germany.

This article has been cited by other articles:

				S. Halak, T. Basta, S. Burger, M. Contzen, V. Wray, D. H. Pieper, and A. Stolz 4-Sulfomuconolactone Hydrolases from Hydrogenophaga intermedia S1 and Agrobacterium radiobacter S2 J. Bacteriol., October 1, 2007; 189(19): 6998 - 7006. [Abstract] [Full Text] [PDF]