Phenylacetyl-CoA:acceptor oxidoreductase, a new α-oxidizing enzyme that produces phenylglyoxylate. Assay, membrane localization, and differential production in Thauera aromatica

Abstract

Anaerobic oxidation of phenylalanine and phenylacetate proceeds via α-oxidation of phenylacetyl-CoA to phenylglyoxylate. This four-electron oxidation system was studied in the denitrifying bacterium Thauera aromatica. It is membrane-bound and was solubilized with Triton X-100. The system used dichlorophenolindophenol as an artificial electron acceptor; a spectrophotometric assay was developed. No other products besides phenylglyoxylate and coenzyme A were observed. The enzyme was quite oxygen-insensitive and was inactivated by low concentrations of cyanide. Enzyme activity was induced under denitrifying conditions with phenylalanine and phenylacetate, it was low in cells grown with phenylglyoxylate, and it was virtually absent in cells grown with benzoate and nitrate or after aerobic growth with phenylacetate.