Anaerobic oxidation of phenylacetate and 4-hydroxyphenylacetate to benzoyl-coenzyme A and CO 2 in denitrifying Pseudomonas sp.

摘要: Anaerobic degradation of (4-hydroxy)phenylacetate in denitrifying Pseudomonas sp. was investigated. Evidence is presented for α-oxidation the coenzyme A (CoA)-activated carboxymethyl side chain, a reaction which has not been described. The C6−C2 compounds are degraded to benzoyl-CoA and furtheron CO2 via following intermediates: Phenylacetyl-CoA, phenylglyoxylate, plus CO2; 4-hydroxyphenylacetyl-CoA, 4-hydroxyphenylglyoxylate, 4-hydroxybenzoyl-CoA CO2, benzoyl-CoA. Trace amounts mandelate possibly derived from mandelyl-CoA were detected during phenylacetate vitro. reactions catalyzed by (i) phenylacetate-CoA ligase converts phenylacetyl-CoA second enzyme 4-hydroxyphenylacetate; (ii) (4-hydroxy)-phenylacetyl-CoA dehydrogenase system oxidizes (4-hydroxy)phenylglyoxylate CoA; (iii) (4-hydroxy)phenylglyoxylate: acceptor oxidoreductase (CoA acylating) catalyzes oxidative decarboxylation (4-hydroxy)benzoyl-CoA CO2. (iv) 4-hydroxyphenylacetate addition requires reductive dehydroxylation benzoyl-CoA, reductase (dehydroxylating). whole cell regulation these activities supports proposed pathway. An ionic mechanism anaerobic CoA-activated chain proposed. Phenylacetic acids plant constituents formed large variety natural aromatic microorganisms; their therefore plays significant role nature, as illustrated preceding paper (Mohamed Fuchs 1993). We have investigated purified an first step Phenylacetate converted (AMP forming). postulated function this corroborated strict its expression. 4-Hydroxyphenylacetate appears be similarly activated independent prior further degradation.