Zhao Huabing, Chen Defu, Li Yongjun, Cai Baoli
Department of Microbiology, Nankai University, Tianjin 300071, China.
Microbiol Res. 2005;160(3):307-13. doi: 10.1016/j.micres.2005.02.004.
A new salicylate hydroxylase from naphthalene-degrading Pseudomonas sp. strain ND6, NahU, has been identified. The nahU is an isofunctional gene of the classic salicylate hydroxylase gene, nahG, and situated outside the transcriptional unit forming the naphthalene degradation lower pathway. Both genes, nahU and nahG of Pseudomonas sp. ND6, have been cloned and overexpressed in Escherichia coli BL21 (DE3). NahU contains 429 amino acid residues and NahG contains 434 amino acid residues. SDS-PAGE analysis showed that both NahG and NahU are about 47 kDa. Both enzymes exhibit broad substrate specificities and metabolize salicylate, sulfosalicylate, aspirin, methylsalicylate, chlorosalicylate and 3,5-dinitrosalicylate. The comparison of the Km and Vmax values for NahG and NahU demonstrated that NahU possesses a higher binding ability to salicylate and cofactors and catalytic efficiency.
已鉴定出一种来自萘降解假单胞菌属菌株ND6的新型水杨酸羟化酶NahU。nahU是经典水杨酸羟化酶基因nahG的同功能基因，位于形成萘降解下游途径的转录单元之外。假单胞菌属ND6的nahU和nahG这两个基因均已在大肠杆菌BL21(DE3)中克隆并过表达。NahU含有429个氨基酸残基，NahG含有434个氨基酸残基。SDS-PAGE分析表明，NahG和NahU的分子量均约为47 kDa。这两种酶均表现出广泛的底物特异性，可代谢水杨酸、磺基水杨酸、阿司匹林、水杨酸甲酯、氯水杨酸和3,5-二硝基水杨酸。NahG和NahU的Km和Vmax值比较表明，NahU对水杨酸和辅因子具有更高的结合能力和催化效率。
