Anaerobic metabolism of l-phenylalanine via benzoyl-CoA in the denitrifying bacterium Thauera aromatica |
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Authors: | Sabine Schneider M E-S Mohamed G Fuchs |
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Institution: | Mikrobiologie, Institut Biologie II, Universit?t Freiburg, Sch?nzlestr. 1, D-79104 Freiburg, Germany Tel. +49-761-203-2649; Fax +49-761-203–2626 e-mail: fuchsgeo@ruf.uni-freiburg.de, DE
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Abstract: | The anaerobic metabolism of phenylalanine was studied in the denitrifying bacterium Thauera aromatica, a member of the β-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 α-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.
Received: 6 March 1997 / Accepted: 16 May 1997 |
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Keywords: | Thauera aromatica l-phenylalanine metabolism Phenylalanine transaminase Phenylpyruvate decarboxylase Phenylacetaldehyde dehydrogenase Phenylacetate-CoA ligase α -Oxidation of phenylacetyl-CoA Phenylglyoxylate:acceptor oxidoreductase |
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