title: Anaerobic metabolism of L-phenylalanine via benzoyl-CoA in the denitrifying bacterium Thauera aromatica.
abstract: The anaerobic metabolism of phenylalanine was studied in the denitrifying bacterium Thauera aromatica, a member of the beta-subclass of the Proteobacteria. Phenylalanine was completely oxidized and served as the sole source of cell carbon. Evidence is presented that degradation proceeds via benzoyl-CoA as the central aromatic intermediate; the aromatic ring-reducing enzyme benzoyl-CoA reductase was present in cells grown on phenylalanine. Intermediates in phenylalanine oxidation to benzoyl-CoA were phenylpyruvate, phenylacetaldehyde, phenylacetate, phenylacetyl-CoA, and phenylglyoxylate. The required enzymes were detected in extracts of cells grown with phenylalanine and nitrate. Oxidation of phenylalanine to benzoyl-CoA was catalyzed by phenylalanine transaminase, phenylpyruvate decarboxylase, phenylacetaldehyde dehydrogenase (NAD+), phenylacetate-CoA ligase (AMP-forming), enzyme(s) oxidizing phenylacetyl-CoA to phenylglyoxylate with nitrate, and phenylglyoxylate:acceptor oxidoreductase. The capacity for phenylalanine oxidation to phenylacetate was induced during growth with phenylalanine. Evidence is provided that alpha-oxidation of phenylacetyl-CoA is catalyzed by a membrane-bound enzyme. This is the first report on the complete anaerobic degradation of an aromatic amino acid and the regulation of this process.
authors.affiliation: Mikrobiologie, Institut Biologie II, Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schneider
authors.forename: M E
authors.initials: ME
authors.lastname: Mohamed
authors.forename: G
authors.initials: G
authors.lastname: Fuchs
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives / Q000378:metabolism; D000105:Acetyl Coenzyme A / Q000378:metabolism; D000214:Acyl Coenzyme A / Q000378:metabolism*; D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D000693:Anaerobiosis; D001565:Benzoates / Q000378:metabolism; D019817:Benzoic Acid; D002262:Carboxy-Lyases / Q000378:metabolism; D003066:Coenzyme A Ligases / Q000378:metabolism; D029968:Escherichia coli Proteins; D016965:Gram-Negative Anaerobic Straight, Curved, and Helical Rods / Q000378:metabolism*; D007658:Ketone Oxidoreductases / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010648:Phenylacetates / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism*; D000637:Transaminases / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D001565:Benzoates; D029968:Escherichia coli Proteins; D009566:Nitrates; D010648:Phenylacetates; D009243:NAD; D010649:Phenylalanine; C037817:benzoyl-coenzyme A; D000105:Acetyl Coenzyme A; C037816:phenylacetyl-coenzyme A; D019817:Benzoic Acid; D010088:Oxidoreductases; D000445:Aldehyde Oxidoreductases; D007658:Ketone Oxidoreductases; C053855:phenylacetaldehyde dehydrogenase; C109059:phenylglyoxylate - acceptor oxidoreductase; D044925:Oxidoreductases Acting on CH-CH Group Donors; C109030:benzoyl-coenzyme A reductase (dearomatizing); D000637:Transaminases; D002262:Carboxy-Lyases; C109058:phenylpyruvate decarboxylase; D003066:Coenzyme A Ligases; C023914:phenylacetate - CoA ligase; C025136:phenylacetic acid; D000079:Acetaldehyde; C013192:phenylacetaldehyde