Erickson B D, Mondello F J
Environmental Laboratory, General Electric Co., Schenectady, New York 12301.
Appl Environ Microbiol. 1993 Nov;59(11):3858-62. doi: 10.1128/aem.59.11.3858-3862.1993.
Biphenyl dioxygenase catalyzes the first step in the aerobic degradation of polychlorinated biphenyls (PCBs). The nucleotide and amino acid sequences of the biphenyl dioxygenases from two PCB-degrading strains (Pseudomonas sp. strain LB400 and Pseudomonas pseudoalcaligenes KF707) were compared. The sequences were found to be nearly identical, yet these enzymes exhibited dramatically different substrate specificities for PCBs. Site-directed mutagenesis of the LB400 bphA gene resulted in an enzyme combining the broad congener specificity of LB400 with increased activity against several congeners characteristic of KF707. These data strongly suggest that the BphA subunit of biphenyl dioxygenase plays an important role in determining substrate selectivity. Further alteration of this enzyme can be used to develop a greater understanding of the structural basis for congener specificity and to broaden the range of degradable PCB congeners.
联苯双加氧酶催化多氯联苯（PCBs）好氧降解的第一步。比较了两种降解PCBs菌株（假单胞菌属LB400菌株和假产碱假单胞菌KF707）中联苯双加氧酶的核苷酸和氨基酸序列。发现这些序列几乎相同，但这些酶对PCBs表现出显著不同的底物特异性。对LB400 bphA基因进行定点诱变，得到了一种酶，它结合了LB400广泛的同系物特异性和对几种KF707特征性同系物的活性增加。这些数据有力地表明，联苯双加氧酶的BphA亚基在决定底物选择性方面起着重要作用。对该酶的进一步改造可用于更深入地了解同系物特异性的结构基础，并拓宽可降解PCBs同系物的范围。
