柴油食烷菌B-5及其卤代烷烃脱卤酶DadA对卤代化合物的降解

Degradation of halogenated compounds by haloalkane dehalogenase DadA from Alcanivorax dieselolei B-5

摘要:

摘要:【目的】柴油食烷菌(Alcanivorax dieselolei)B-5是重要的石油降解菌。为研究其对卤代化合物的降解范围和降解机制，【方法】以不同的卤代化合物作为唯一碳源，观察菌株B-5在其中的生长情况;通过多重序列比对、系统发育分析和三维结构同源建模，分析该菌株基因组内一个假定的卤代烷烃脱卤酶(Haloalkane dehalogenase，HLD)DadA;利用大肠杆菌异源表达、纯化DadA，并测定了其对46个卤代底物的酶活。【结果】菌株B-5能够利用C3-C18链长范围的多种卤代化合物为唯一碳源生长;在系统进化树中，DadA相对独立于其他HLD-II亚家族成员，但具有典型的HLD-II亚家族的催化五联体残基;DadA确实具有脱卤活性，但该酶特异性高，底物范围明显小于其他已鉴定的HLDs，仅对1，2，3-三溴丙烷、1，2-二溴-3-氯丙烷和2，3-二氯-1-丙烯有脱卤酶活。【结论】因为DadA对很多B-5菌株可以利用做碳源的卤代底物没有脱卤酶活，所以推测 B-5菌中可能还有其他脱卤酶参与了卤代烷烃的降解。菌株B-5及其卤代烷烃脱卤酶DadA在卤代烷烃污染物的生物降解方面具有应用潜力。

Abstract:

Abstract:［Objective］Alcanivorax dieselolei B-5 is an important oil-degrading bacterium．We studied its substrate range and degradation of halogenated compounds．［Methods］Growth capability of B-5 was examined with different halogenated substrates as sole carbon source．A putative haloalkane dehalogenase (HLD) gene named dadA was found from the genome of strain B-5 and analyzed by sequence alignment，phylogenetic analysis and homologous modeling．After heterologous expression in Escherichia coli and purification，the activity of DadA towards 46 substrates was determined．［Results］Strain B-5 was capable of utilizing various halogenated compounds (C3 -C18) as the sole carbon source．DadA had typical catalytic pentad residues of HLD-II subfamily，but it was independent from other members of this subfamily according to phylogenetic analysis． Activity assay showed that DadA has higher specificity and narrower substrate range than other characterized HLDs and it only showed activity toward 1，2，3-tribromopropane，1，2-dibromo-3-chloropropane and 2，3-dichloroprop-1-ene among 46 tested substrates．［Conclusions］ Strain B-5 and its HLD DadA can degrade halogenated aliphatic pollutants although．