Substitution of the ISP alpha subunit of biphenyl dioxygenase from Pseudomonas results in a modification of the enzyme activity.

We have constructed a hybrid multicomponent dioxygenase gene cluster in which the bphA1 gene, coding for ISP alpha subunit of biphenyl dioxygenase from Pseudomonas pseudoalcaligenes KF707, has been replaced by the bedC1 gene encoding the corresponding subunit of benzene dioxygenase from P. putida ML2. Escherichia coli cells containing the chimeric dioxygenase acquired the novel capability of producing indigo from indole. Furthermore, when compared to biphenyl dioxygenase, the hybrid dioxygenase enzyme was half as active towards benzene but exhibited only 4% activity when biphenyl was the substrate. The results implicate the ISP alpha subunit to be involved in substrate specificity and activity of the dioxygenase enzyme.