Biphenyl dioxigenase is known as an initial key enzyme to degrade environmental pollutants, which are derived from coal and petroleum (mainly polycyclic aromas). The genes coding for this enzyme are ordinarily composed of four gene components (bphA1A2A3A4). The bphA1 genes encoding the large (α) subunit of this enzyme was modified by DNA shuffling between the corresponding genes of Pseudomonas pseudoalcaligenes KF707 and Burkholderia cepacia LB400. Among them, we found a gene [bphA1 (2072)] that codes for a large subunit with extremely broad substrate specificity. The biphenyl dioxygenase genes including this modified bphA1 (modified bphA1: bphA2A3A4) were introduced into bacteria Escherichia coli and Streptomyces lividans on vectors pUC118 and pIJ6021, respectively. Using these recombinant bacteria, we succeeded in converting many heterocyclic aromatic compounds to the corresponding 1,2-dihydrodiol and/or monohydroxy derivatives with high efficacy. Even the aromatic compounds containing primary amine were able to be converted by protecting the amine as phthalic imide. Probably in many cases, the above biological technique is a simpler and effective method compared with the case synthesized by organic chemistry. Furthermore, it would be possible to complements the methods of combinatorial chemistry through extending the applicable category of the biotechnological method shown in this article. In the near future, we would like to aim at the establishment of the biological technologies that we call "BioCombiChem" (Biology-based Combinatorial Chemistry).
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