tailieunhanh - Báo cáo khoa học: Functional genomics by NMR spectroscopy Phenylacetate catabolism in Escherichia coli

Aerobic metabolism of phenylalanine in most bacteria proceeds via oxidation to phenylacetate. Surprisingly, the further metabolism of phenylacetate has not been elucida-ted, even in well studied bacteria such as Escherichia coli. The only committed step is the conversion of phenylacetate into phenylacetyl-CoA. The paaoperon ofE. coliencodes 14 polypeptides involved in the catabolismof phenylacetate. We have found thatE. | Eur. J. Biochem. 270 3047-3054 2003 FEBS 2003 doi Functional genomics by NMR spectroscopy Phenylacetate catabolism in Escherichia coli Wael Ismail1 Magdy El-Said Mohamed1 Barry L. Wanner2 Kirill A. Datsenko2 Wolfgang Eisenreich3 Felix Rohdich3 Adelbert Bacher3 and Georg Fuchs1 1Mikrobiologie Institut fur Biologie II Universitat Freiburg Germany department of Biological Sciences Purdue University West Lafayette IN USA 3Lehrstuhl fur Organische Chemie und Biochemie Tcchnische Universttdt Munchen Germany Aerobic metabolism of phenylalanine in most bacteria proceeds via oxidation to phenylacetate. Surprisingly the further metabolism of phenylacetate has not been elucidated even in well studied bacteria such as Escherichia coli. The only committed step is the conversion of phenylacetate into phenylacetyl-CoA. The paa operon of E. coli encodes 14 polypeptides involved in the catabolism of phenylacetate. We have found that E. coli K12 mutants with a deletion of the paaF paaG paaH paaJ or paaZ gene are unable to grow with phenylacetate as carbon source. Incubation of a paaG mutant with U-13C8 phenylacetate yielded ring-1 2-dihydroxy-1 2-dihydrophenylacetyl lactone as shown by NMR spectroscopy. Incubation of the paaF and paaH mutants with phenylacetate yielded A3-dehydroadipate and 3-hydroxyadipate respectively. The origin of the carbon atoms of these C6 compounds from the aromatic ring was shown using ring-13C6 phenylacetate. The paaG and paaZ mutants also converted phenylacetate into ortho-hydroxy-phenylacetate which was previously identified as a dead end product of phenylacetate catabolism. These data in conjunction with protein sequence data suggest a novel catabolic pathway via CoA thioesters. According to this phenylacetyl-CoA is attacked by a ring-oxygenase reductase PaaABCDE proteins generating a hydroxylated and reduced derivative of phenylacetyl-CoA which is not re-oxidized to a dihydroxylated aromatic intermediate as in other .

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