Biochemistry and genetics of the pathway for the anaerobic degradation of aromatic compounds by Eubacterium oxidoreducens
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Mutant strains of E. oxidoreducens that showed no gallate decarboxylase or dihydrophloroglucinol hydrolase activity were isolated after mutagenesis with ethylmethane sulfonate and emichment with ampicillin. The decarboxylase deficient mutants were unable to grow on gallate while pyrogallol and phloroglucinol supported growth. The hydrolase deficient mutants were unable to grow on any aromatic substrates and converted gallate to pyrogallol and dihydrophloroglucinol. The conversion of gallate to non-aromatic intermediates by cell extract of the wild-type stain was dependent on the presence of 1,2,3,5-benzenetetrol for the conversion of pyrogallol to phloroglucinol and on formate for the reduction of phloroglucinol to dihydrophloroglucinol. Transhydroxylase activity involved in the conversion of pyrogallol to phloroglucinol was induced by growth on aromatic substrates. The formate dehydrogenase was located in the soluble fraction of cell extract, and activity was protected from oxygen inactivation by sodium azide. The Km for formate and NADP was 290 Î¼M and 140 Î¼M respectively at pH 7.5. The pH optimum for activity was 7.5 and maximum activity was observed at a temperature of 50Â° C.
- Doctoral Dissertations