Characterization of genes involved in the initial reactions of 4-chloronitrobenzene degradation in Pseudomonas putida ZWL73.
The genes encoding enzymes involved in the initial reactions during degradation of 4-chloronitrobenzene (4CNB) were characterized from the 4CNB utilizer Pseudomonas putida ZWL73, in which a partial reductive pathway was adopted. A DNA fragment containing genes coding for chloronitrobenzene nitroreductase (CnbA) and hydroxylaminobenzene mutase (CnbB) were PCR-amplified and subsequently sequenced. These two genes were actively expressed in Escherichia coli, and recombinant E. coli cells catalyzed the conversion of 4CNB to 2-amino-5-chlorophenol, which is the ring-cleavage substrate in the degradation of 4CNB. Phylogenetic analyses on sequences of chloronitrobenzene nitroreductase and hydroxylaminobenzene mutase revealed that these two enzymes are closely related to the functionally identified nitrobenzene nitroreductase and hydroxylaminobenzene mutase from Pseudomonas strains JS45 and HS12. The nitroreductase from strain ZWL73 showed a higher specific activity toward 4CNB than nitrobenzene (approximately at a ratio of 1.6:1 for the recombinant or 2:1 for the wild type), which is in contrast to the case where the nitroreductase from nitrobenzene utilizers Pseudomonas pseudoalcaligenes JS45 with an apparently lower specific activity against 4CNB than nitrobenzene (0.16:1) [Kadiyala et al. Appl Environ Microbiol 69:6520-6526, 2003]. This suggests that the nitroreductase from 4-chloronitrobenzene utilizer P. putida ZWL73 may have evolved to prefer chloronitrobenzene to nitrobenzene as its substrate.
Xiao
Yi
Y
Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China.
Wu
Jian-Feng
JF
Liu
Hong
H
Wang
Shu-Jun
SJ
Liu
Shuang-Jiang
SJ
Zhou
Ning-Yi
NY
D001426:Bacterial Proteins / Q000235:genetics; D001673:Biodegradation, Environmental; D002733:Chlorophenols / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D019751:Intramolecular Transferases / Q000235:genetics; D008969:Molecular Sequence Data; D009578:Nitrobenzenes / Q000378:metabolism*; D009601:Nitroreductases / Q000235:genetics; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D016958:Pseudomonas putida / Q000201:enzymology* / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D001426:Bacterial Proteins; D002733:Chlorophenols; D004269:DNA, Bacterial; D009578:Nitrobenzenes; C099673:2-amino-5-chlorophenol; C010407:4-chloronitrobenzene; C036077:nitrobenzene; D009601:Nitroreductases; D019751:Intramolecular Transferases; C412734:hydroxylaminobenzene mutase