Biosynthesis of Proteus mirabilis nuclease

The culture liquid and periplasm of Proteus mirabilis contained nuclease, a n enzyme with DNase and RNase activities. The nuclease was most actively sy nthesized in the early exponential and stationary growth phases. Nuclease s ynthesis was regulated by nucleic acids (induction by substrate) and inorga nic phosphate tend-product inhibition). The synthesis and secretion of nucl ease by P. mirabilis was induced by mitomycin C, an inducer of the SOS func tions of cells. This suggests the involvement of SOS-response proteins in t he regulation of nuclease synthesis.