EVIDENCE THAT PHENOL PHOSPHORYLATION TO PHENYLPHOSPHATE IS THE FIRST STEP IN ANAEROBIC PHENOL METABOLISM IN A DENITRIFYING PSEUDOMONAS SP

Anaerobic phenol degradation has been shown to proceed via carboxylati on of phenol to 4-hydroxybenzoate. However, in vitro the carboxylating enzyme was inactive with phenol; only phenylphosphate (phosphoric aci d monophenyl ester) was readily carboxylated. We demonstrate in a deni trifying Pseudomonas strain that phenylphosphate ist he first detectab le product formed from phenol in whole cells and that subsequent pheny l-phosphate consumption parallels 4-hydroxybenzoate formation. These k inetics are consistent with phosphorylation being the first step in an aerobic phenol degradation. Various cosubstrates failed so far to act as phosphoryl donor for net phosphorylation of phenol in cell extracts . Yet, cells anaerobically grown with phenol contained an enzyme that catalyzed an isotope exchange between [U-C-14]phenol and phenylphospha te. This transphosphorylation activity was anaerobically induced by ph enol but was stable under aerobic conditions and required Mn2+ and pol yethylene glycol. Activity was optimal at pH 5.5 and half-maximal with 0.6 mM Mn2+, 0.2 mM phenylphosphate, and 1 mM phenol. It is proposed that the phenol exchange/transphosphorylation reaction is catalyzed as partial reaction by an inducible phenol phosphorylating enzyme. The i sotope exchange demands that a phosphorylated enzyme was formed in the course of the reaction, which might be similar to the phosphotransfer ase system of sugar transport.