O-phthalic acid, a dead-end product in one of the two pathways of phenanthrene degradation in Pseudomonas sp. strain PP2.
Phenanthrene is degraded via either o-phthalic acid or 1, 2-dihydroxynaphthalene in bacteria. A soil isolate Pseudomonas sp. strain PP2 degrades phenanthrene as the sole source of carbon, but failed to utilize naphthalene [Prabhu and Phale (2003) Appl Microbiol Biotechnol 61:342-351]. Analysis of the phenanthrene-grown culture spent media of this strain by gas chromatography-mass spectrometry (GC-MS) showed accumulation of o-phthalic acid. The cell-free extract prepared from this strain showed activity of 1-hydroxy-2-naphthoic acid dioxygenase (1-H-2-NADO). The extract showed conversion of 1-hydroxy-2-naphthoic acid and 2-carboxybenzaldehyde to o-phthalic acid, as analyzed by thin layer chromatography and GC-MS. However, it failed to grow or respire on o-phthalic acid. These results suggest that besides 1, 2-dihydroxynaphthalene pathway, the strain has a truncated o-phthalic acid pathway for phenanthrene metabolism and excretes o-phthalic acid as a dead-end product, indicating the co-existence of two pathways. 1-H-2-NADO, the key enzyme of o-phthalic acid pathway is inducible, has pH optima of 7.5, does not require external addition of Fe(II) as a co-factor and is completely inhibited by 1,10-phenanthroline. Absence of product formation under anaerobic condition and stoichiometric consumption of 0.82 moles of O2 per mole of product formed confirmed the dioxygenase nature of the enzyme.
Biotechnology Group, School of Biosciences and Bioengineering, Indian Institute of Technology-Bombay, Mumbai 400 076, India.
Samyuktha
S
Krishnan
Yogikala
Y
Prabhu
Prashant S
PS
Phale
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001671:Biochemistry / Q000379:methods; D002474:Cell-Free System; D002614:Chelating Agents / Q000494:pharmacology; D002855:Chromatography, Thin Layer / Q000379:methods; D049308:Dioxygenases / Q000737:chemistry / Q000378:metabolism*; D004798:Enzymes / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000737:chemistry; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry; D010616:Phenanthrenes / Q000737:chemistry / Q000378:metabolism*; D010795:Phthalic Acids / Q000737:chemistry*; D011549:Pseudomonas / Q000378:metabolism*; D013053:Spectrophotometry / Q000379:methods; D013997:Time Factors
D001426:Bacterial Proteins; D002614:Chelating Agents; D004798:Enzymes; D008670:Metals; D010616:Phenanthrenes; D010795:Phthalic Acids; C031181:phenanthrene; C032279:phthalic acid; C574975:1-hydroxy-2-naphthoic acid dioxygenase, Pseudomonas sp. strain PP2; D049308:Dioxygenases; D010100:Oxygen