Novel partial reductive pathway for 4-chloronitrobenzene and nitrobenzene degradation in Comamonas sp. strain CNB-1.
Comamonas sp. strain CNB-1 grows on 4-chloronitrobenzene (4-CNB) and nitrobenzene as sole carbon and nitrogen sources. In this study, two genetic segments, cnbB-orf2-cnbA and cnbR-orf1-cnbCaCbDEFGHI, located on a newly isolated plasmid, pCNB1 (ca. 89 kb), and involved in 4-CNB/nitrobenzene degradation, were characterized. Seven genes (cnbA, cnbB, cnbCa, cnbCb, cnbD, cnbG, and cnbH) were cloned and functionally expressed in recombinant Escherichia coli, and they were identified as encoding 4-CNB nitroreductase (CnbA), 1-hydroxylaminobenzene mutase (CnbB), 2-aminophenol 1,6-dioxygenase (CnbCab), 2-amino-5-chloromuconic semialdehyde dehydrogenase (CnbD), 2-hydroxy-5-chloromuconic acid (2H5CM) tautomerase, and 2-amino-5-chloromuconic acid (2A5CM) deaminase (CnbH). In particular, the 2A5CM deaminase showed significant identities (31 to 38%) to subunit A of Asp-tRNAAsn/Glu-tRNAGln amidotransferase and not to the previously identified deaminases for nitroaromatic compound degradation. Genetic cloning and expression of cnbH in Escherichia coli revealed that CnbH catalyzed the conversion of 2A5CM into 2H5CM and ammonium. Four other genes (cnbR, cnbE, cnbF, and cnbI) were tentatively identified according to their high sequence identities to other functionally identified genes. It was proposed that CnbH might represent a novel type of deaminase and be involved in a novel partial reductive pathway for chloronitrobenzene or nitrobenzene degradation.
Wu
Jian-feng
JF
State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
Jiang
Cheng-ying
CY
Wang
Bao-jun
BJ
Ma
Ying-fei
YF
Liu
Zhi-pei
ZP
Liu
Shuang-jiang
SJ
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001673:Biodegradation, Environmental; D003001:Cloning, Molecular; D020585:Comamonas / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D009578:Nitrobenzenes / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny; D010957:Plasmids; D017422:Sequence Analysis, DNA
D001426:Bacterial Proteins; D009578:Nitrobenzenes; C010407:4-chloronitrobenzene; C036077:nitrobenzene