Anaerobic oxidation of phenylacetate and 4-hydroxyphenylacetate to benzoyl-coenzyme A and CO2 in denitrifying Pseudomonas sp. Evidence for an alpha-oxidation mechanism.
Anaerobic degradation of (4-hydroxy)phenylacetate in denitrifying Pseudomonas sp. was investigated. Evidence is presented for alpha-oxidation of 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 to CO2 via the following intermediates: Phenylacetyl-CoA, phenylglyoxylate, benzoyl-CoA plus CO2; 4-hydroxyphenylacetyl-CoA, 4-hydroxyphenylglyoxylate, 4-hydroxybenzoyl-CoA plus CO2, benzoyl-CoA. Trace amounts of mandelate possibly derived from mandelyl-CoA were detected during phenylacetate degradation in vitro. The reactions are catalyzed by (i) phenylacetate-CoA ligase which converts phenylacetate to phenylacetyl-CoA and by a second enzyme for 4-hydroxyphenylacetate; (ii) a (4-hydroxy)-phenylacetyl-CoA dehydrogenase system which oxidizes phenylacetyl-CoA to (4-hydroxy)phenylglyoxylate plus CoA; and (iii) (4-hydroxy)phenylglyoxylate: acceptor oxidoreductase (CoA acylating) which catalyzes the oxidative decarboxylation of (4-hydroxy)phenylglyoxylate to (4-hydroxy)benzoyl-CoA and CO2. (iv) The degradation of 4-hydroxyphenylacetate in addition requires the reductive dehydroxylation of 4-hydroxybenzoyl-CoA to benzoyl-CoA, catalyzed by 4-hydroxybenzoyl-CoA reductase (dehydroxylating). The whole cell regulation of these enzyme activities supports the proposed pathway. An ionic mechanism for anaerobic alpha-oxidation of the CoA-activated carboxymethyl side chain is proposed.
Mohamed M el-S
Angewandte Mikrobiologie, Universität Ulm, Germany.
Seyfried
B
B
Tschech
A
A
Fuchs
G
G
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000693:Anaerobiosis / Q000502:physiology; D001565:Benzoates / Q000378:metabolism; D001673:Biodegradation, Environmental; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D006038:Glyoxylates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008333:Mandelic Acids; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010648:Phenylacetates / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors
D000214:Acyl Coenzyme A; D001565:Benzoates; D006038:Glyoxylates; D008333:Mandelic Acids; D009566:Nitrates; D009573:Nitrites; D010648:Phenylacetates; C012482:phenylglyoxylic acid; C026246:4-hydroxyphenylacetate; C037817:benzoyl-coenzyme A; C025136:phenylacetic acid