title: Identification of the para-nitrophenol catabolic pathway, and characterization of three enzymes involved in the hydroquinone pathway, in Peudomonas sp. 1-7.
abstract: BACKGROUND
  para-Nitrophenol (PNP), a priority environmental pollutant, is hazardous to humans and animals. However, the information relating to the PNP degradation pathways and their enzymes remain limited.
  
  
  RESULTS
  Pseudomonas sp.1-7 was isolated from methyl parathion (MP)-polluted activated sludge and was shown to degrade PNP. Two different intermediates, hydroquinone (HQ) and 4-nitrocatechol (4-NC) were detected in the catabolism of PNP. This indicated that Pseudomonas sp.1-7 degraded PNP by two different pathways, namely the HQ pathway, and the hydroxyquinol (BT) pathway (also referred to as the 4-NC pathway). A gene cluster (pdcEDGFCBA) was identified in a 10.6 kb DNA fragment of a fosmid library, which cluster encoded the following enzymes involved in PNP degradation: PNP 4-monooxygenase (PdcA), p-benzoquinone (BQ) reductase (PdcB), hydroxyquinol (BT) 1,2-dioxygenase (PdcC), maleylacetate (MA) reductase (PdcF), 4-hydroxymuconic semialdehyde (4-HS) dehydrogenase (PdcG), and hydroquinone (HQ) 1,2-dioxygenase (PdcDE). Four genes (pdcDEFG) were expressed in E. coli and the purified pdcDE, pdcG and pdcF gene products were shown to convert HQ to 4-HS, 4-HS to MA and MA to β-ketoadipate respectively by in vitro activity assays.
  
  
  CONCLUSIONS
  The cloning, sequencing, and characterization of these genes along with the functional PNP degradation studies identified 4-NC, HQ, 4-HS, and MA as intermediates in the degradation pathway of PNP by Pseudomonas sp.1-7. This is the first conclusive report for both 4-NC and HQ- mediated degradation of PNP by one microorganism.
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Haidian District, Beijing 100081, PR China.
authors.forename: Shuangyu
authors.initials: S
authors.lastname: Zhang
authors.forename: Wen
authors.initials: W
authors.lastname: Sun
authors.forename: Li
authors.initials: L
authors.lastname: Xu
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Zheng
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Chu
authors.forename: Jian
authors.initials: J
authors.lastname: Tian
authors.forename: Ningfeng
authors.initials: N
authors.lastname: Wu
authors.forename: Yunliu
authors.initials: Y
authors.lastname: Fan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002853:Chromatography, Liquid; D004785:Environmental Pollutants / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D023061:Gene Order; D006873:Hydroquinones / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009596:Nitrophenols / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D004785:Environmental Pollutants; D006873:Hydroquinones; D009596:Nitrophenols; D010088:Oxidoreductases