title: Enzymes involved in the anaerobic degradation of ortho-phthalate by the nitrate-reducing bacterium Azoarcus sp. strain PA01.
abstract: The pathway of anaerobic degradation of o-phthalate was studied in the nitrate-reducing bacterium Azoarcus sp. strain PA01. Differential two-dimensional protein gel profiling allowed the identification of specifically induced proteins in o-phthalate-grown compared to benzoate-grown cells. The genes encoding o-phthalate-induced proteins were found in a 9.9 kb gene cluster in the genome of Azoarcus sp. strain PA01. The o-phthalate-induced gene cluster codes for proteins homologous to a dicarboxylic acid transporter, putative CoA-transferases and a UbiD-like decarboxylase that were assigned to be specifically involved in the initial steps of anaerobic o-phthalate degradation. We propose that o-phthalate is first activated to o-phthalyl-CoA by a putative succinyl-CoA-dependent succinyl-CoA:o-phthalate CoA-transferase, and o-phthalyl-CoA is subsequently decarboxylated to benzoyl-CoA by a putative o-phthalyl-CoA decarboxylase. Results from in vitro enzyme assays with cell-free extracts of o-phthalate-grown cells demonstrated the formation of o-phthalyl-CoA from o-phthalate and succinyl-CoA as CoA donor, and its subsequent decarboxylation to benzoyl-CoA. The putative succinyl-CoA:o-phthalate CoA-transferase showed high substrate specificity for o-phthalate and did not accept isophthalate, terephthalate or 3-fluoro-o-phthalate whereas the putative o-phthalyl-CoA decarboxylase converted fluoro-o-phthalyl-CoA to fluoro-benzoyl-CoA. No decarboxylase activity was observed with isophthalyl-CoA or terephthalyl-CoA. Both enzyme activities were oxygen-insensitive and inducible only after growth with o-phthalate. Further degradation of benzoyl-CoA proceeds analogous to the well-established anaerobic benzoyl-CoA degradation pathway of nitrate-reducing bacteria.
authors.affiliation: Konstanz Research School of Chemical Biology, University of Konstanz, Konstanz, D-78457, Germany. madan.junghare@uni-konstanz.de.|Department of Biology, Microbial Ecology, University of Konstanz, Konstanz, D-78457, Germany. madan.junghare@uni-konstanz.de.
authors.forename: Madan
authors.initials: M
authors.lastname: Junghare
authors.affiliation: Konstanz Research School of Chemical Biology, University of Konstanz, Konstanz, D-78457, Germany.|Department of Biology, Chemical Ecology, University of Konstanz, Konstanz, D-78457, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Spiteller
authors.affiliation: Konstanz Research School of Chemical Biology, University of Konstanz, Konstanz, D-78457, Germany.|Department of Biology, Microbial Ecology, University of Konstanz, Konstanz, D-78457, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schink
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000693:Anaerobiosis; D020627:Azoarcus / Q000737:chemistry / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001565:Benzoates / Q000378:metabolism; D005810:Multigene Family; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction; D010795:Phthalic Acids / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D000214:Acyl Coenzyme A; D001426:Bacterial Proteins; D001565:Benzoates; D009566:Nitrates; D010795:Phthalic Acids; C059768:isophthalate; C037817:benzoyl-coenzyme A; C032279:phthalic acid; C012046:succinyl-coenzyme A