A novel deaminase involved in chloronitrobenzene and nitrobenzene degradation with Comamonas sp. strain CNB-1.
Comamonas sp. strain CNB-1 degrades nitrobenzene and chloronitrobenzene via the intermediates 2-aminomuconate and 2-amino-5-chloromuconate, respectively. Deamination of these two compounds results in the release of ammonia, which is used as a source of nitrogen for bacterial growth. In this study, a novel deaminase was purified from Comamonas strain CNB-1, and the gene (cnbZ) encoding this enzyme was cloned. The N-terminal sequence and peptide fingerprints of this deaminase were determined, and BLAST searches revealed no match with significant similarity to any functionally characterized proteins. The purified deaminase is a monomer (30 kDa), and its V(max) values for 2-aminomuconate and 2-amino-5-chloromuconate were 147 micromol x min(-1) x mg(-1) and 196 micromol x min(-1) x mg(-1), respectively. Its catalytic products from 2-aminomuconate and 2-amino-5-chloromuconate were 2-hydroxymuconate and 2-hydroxy-5-chloromuconate, respectively, which are different from those previously reported for the deaminases of Pseudomonas species. In the catalytic mechanism proposed, the alpha-carbon and nitrogen atoms (of both 2-aminomuconate and 2-amino-5-chloromuconate) were simultaneously attacked by a hydroxyl group and a proton, respectively. Homologs of cnbZ were identified in the genomes of Bradyrhizobium japonicum, Rhodopseudomonas palustris, and Roseiflexus sp. strain RS-1; these genes were previously annotated as encoding hypothetical proteins of unknown function. It is concluded that CnbZ represents a novel enzyme that deaminates xenobiotic compounds and/or alpha-amino acids.
Liu
Lei
L
Institute of Microbiology, Chinese Academy of Sciences, ZhongGuanCun, Haidian, Beijing 100080, People's Republic of China.
Wu
Jian-Feng
JF
Ma
Ying-Fei
YF
Wang
Sheng-Yue
SY
Zhao
Guo-Ping
GP
Liu
Shuang-Jiang
SJ
D000595:Amino Acid Sequence; D000619:Aminohydrolases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D020585:Comamonas / Q000201:enzymology*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D009578:Nitrobenzenes / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry; D011549:Pseudomonas / Q000201:enzymology; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D001426:Bacterial Proteins; D009578:Nitrobenzenes; D010446:Peptide Fragments; D011994:Recombinant Proteins; C010407:4-chloronitrobenzene; C036077:nitrobenzene; D000619:Aminohydrolases