中文摘要：

从7个萘降解菌株和5个苯酚降解菌株中经PCR扩增得到12个儿茶酚2，3-双加氧酶（C230）基因，大小均为924bp．根据DNA序列的类似性，可将这12个C230基因聚类为3组，此结果与分离菌株的样本来源基本一致．这12个基因均编码307个氨基酸残基的儿茶酚2，3-双加氧酶，序列中都含有9个严格保守的氨基酸残基（Gly30、His153、Leu172、His199、His214、His246、Tyr255、Pr0259、Glu265），均属于外切双加氧酶的1．2．A亚家族．通过盒式PCR，用各种萘和苯酚降解菌的C230基因中心区替换恶臭假单胞菌ND6菌株pND6—1质粒中nahH基因的中心区，得到5个杂种C230基因，这些基因在pET～E．coliBL21（DE3）系统中表达以后，均能检测到C230活性，其中中心区来自假单胞菌ND24菌株C230基因的杂种酶C230-ND24，其比活力高于对照恶臭假单胞菌ND6菌株的野生型C230．

英文摘要：

Twelve catechol 2, 3-dioxygenase genes from seven naphthalene-degrading strains and five phenol-degrading strains were amplified by PCR and sequenced. The length of all the C230 genes are 924 bp. The twelve C230 genes were divided into three groups according to their sequence identity. This result is consistent to the origin of samples in which degradative strains were isolated. The twelve genes code for catechol 2,3-dioxygenase containing 307 amino acid residues. Among these amino acid residues, the nine are high conservative （Gly30, His153, Leu172, His199, His214, His246, Tyr255, Pro259 and Glu265）. These C23Os belong to 1. 2. A subfamily of extradiol dioxygenases. Five hybrid C230 genes were constructed by cassette PCR in which central segments of C230 genes from environmental samples were isolated and replaced the corresponding nahH sequence from plasmid pND6-1 of Pseudomonas putida ND6. These hybrid C230 genes could express active catechol 2,3-dioxygenase in pET-E, coli BL21（DE3） system. Among them, the hybrid enzyme C230-ND24 that central segment was from naphthalene-degrading Pseudornonas sp. ND24 exhibited higher specific activity than that of wild-type C230 from Pseudomonas 2utida ND6.