title: Influence of para-substituents on the oxidative metabolism of o-nitrophenols by Pseudomonas putida B2.
abstract: Pseudomonas putida B2 is able to grow on o-nitrophenol (ONP) as the sole source of carbon and nitrogen. ONP was converted by a nitrophenol oxygenase to nitrite and catechol. Catechol was then attacked by a catechol 1,2-dioxygenase and further degraded through an ortho-cleavage pathway. ONP derivatives which were para-substituted with a methyl-, chloro-, carboxy-, formyl- or nitro-group failed to support growth of strain B2. Relevant catabolic enzymes were characterized to analyze why these derivatives were not mineralized. Nitrophenol oxygenase of strain B2 is a soluble, NADPH-dependent enzyme that is stimulated by magnesium, manganese, and calcium ions. It is active toward ONP, 4-methyl-, 4-chloro-, and to a lesser extent, 4-formyl-ONP but not toward 4-carboxy- or 4-nitro-ONP. In addition, 4-formyl-, 4-carboxy-, and 4-nitro-ONP failed to induce the formation of nitrophenol oxygenase. Catechol 1,2-dioxygenase of strain B2 is active toward catechol and 4-methyl-catechol but only poorly active toward chlorinated catechols. 4-Methyl-catechol is likely to be degraded to methyl-lactones, which are often dead-end metabolites in bacteria. Thus, of the compounds tested, only unsubstituted ONP acts as an inducer and substrate for all of the enzymes of a productive catabolic pathway.
mesh_terms: D050548:Catechol 1,2-Dioxygenase; D049308:Dioxygenases; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009596:Nitrophenols / Q000378:metabolism* / Q000494:pharmacology; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000378:metabolism*; D011549:Pseudomonas / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D009596:Nitrophenols; D006899:Mixed Function Oxygenases; D010105:Oxygenases; D049308:Dioxygenases; D050548:Catechol 1,2-Dioxygenase; C055456:2-nitrophenol oxygenase