Initial reactions in anaerobic oxidation of m-xylene by the denitrifying bacterium Azoarcus sp. strain T.

TitleInitial reactions in anaerobic oxidation of m-xylene by the denitrifying bacterium Azoarcus sp. strain T.
Publication TypeJournal Article
Year of Publication1999
AuthorsKrieger, CJ, Beller HR, Reinhard M, Spormann AM
JournalJournal of bacteriology
Volume181
Issue20
Pagination6403-10
Date Published1999 Oct
ISSN0021-9193
KeywordsAnaerobiosis, Azoarcus, Benzoic Acids, Biodegradation, Environmental, Cell Membrane Permeability, Molecular Sequence Data, Nitrates, Nitrites, Oxidation-Reduction, Phylogeny, RNA, Bacterial, RNA, Ribosomal, 16S, Toluene, Xylenes
AbstractThe initial enzymatic steps in anaerobic m-xylene oxidation were studied in Azoarcus sp. strain T, a denitrifying bacterium capable of mineralizing m-xylene via 3-methylbenzoate. Permeabilized cells of m-xylene-grown Azoarcus sp. strain T catalyzed the addition of m-xylene to fumarate to form (3-methylbenzyl)succinate. In the presence of succinyl coenzyme A (CoA) and nitrate, (3-methylbenzyl)succinate was oxidized to E-(3-methylphenyl)itaconate (or a closely related isomer) and 3-methylbenzoate. Kinetic studies conducted with permeabilized cells and whole-cell suspensions of m-xylene-grown Azoarcus sp. strain T demonstrated that the specific rate of in vitro (3-methylbenzyl)succinate formation accounts for at least 15% of the specific rate of in vivo m-xylene consumption. Based on these findings, we propose that Azoarcus sp. strain T anaerobically oxidizes m-xylene to 3-methylbenzoate (or its CoA thioester) via (3-methylbenzyl)succinate and E-(3-methylphenyl)itaconate (or its CoA thioester) in a series of reactions that are analogous to those recently proposed for anaerobic toluene oxidation to benzoyl-CoA. A deuterium kinetic isotope effect was observed in the (3-methylbenzyl)succinate synthase reaction (and the benzylsuccinate synthase reaction), suggesting that a rate-determining step in this novel fumarate addition reaction involves breaking a C-H bond.
Alternate JournalJ. Bacteriol.
0 November 24, 2010