Functional genomics by NMR spectroscopy. Phenylacetate catabolism in Escherichia coli.

摘要: Aerobic metabolism of phenylalanine in most bacteria proceeds via oxidation to phenylacetate. Surprisingly, the further phenylacetate has not been elucidated, even well studied such as Escherichia coli. The only committed step is conversion into phenylacetyl-CoA. paa operon E. coli encodes 14 polypeptides involved catabolism We have found that K12 mutants with a deletion paaF, paaG, paaH, paaJ or paaZ gene are unable grow carbon source. Incubation paaG mutant [U-13C8]phenylacetate yielded ring-1,2-dihydroxy-1,2-dihydrophenylacetyl lactone shown by NMR spectroscopy. paaF and paaH Δ3-dehydroadipate 3-hydroxyadipate, respectively. origin atoms these C6 compounds from aromatic ring was using [ring-13C6]phenylacetate. also converted ortho-hydroxyphenylacetate, which previously identified dead end product catabolism. These data, conjunction protein sequence suggest novel catabolic pathway CoA thioesters. According this, phenylacetyl-CoA attacked ring-oxygenase/reductase (PaaABCDE proteins), generating hydroxylated reduced derivative phenylacetyl-CoA, re-oxidized dihydroxylated intermediate, other known pathways. Rather, it proposed this nonaromatic intermediate ester metabolized complex reaction comprising enoyl-CoA isomerization/hydration, nonoxygenolytic opening, dehydrogenation catalyzed PaaG PaaZ proteins. subsequent β-oxidation-type degradation resulting dicarboxylate β-ketoadipyl-CoA succinyl-CoA acetyl-CoA appears be PaaJ, PaaF PaaH