A novel deaminase involved in chloronitrobenzene and nitrobenzene degradation with Comamonas sp strain CNB-1

作者：Liu Lei; Wu Jian Feng; Ma Ying Fei; Wang Sheng Yue; Zhao Guo Ping; Liu Shuang Hang^*

来源：Journal of Bacteriology, 2007, 189(7): 2677-2682.

DOI：10.1128/JB.01762-06

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 mu mol center dot min(-1) center dot mg(-1) and 196 mu mol center dot min(-1) center dot 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.

• 出版日期2007-4
• 单位上海人类基因组研究中心; 中国科学院微生物研究所