DEOXYRIBOENDONUCLEASES WITH EXOCYTOPLASMIC LOCATION IN STREPTOMYCES

DNase activities that show a non-specific pattern of DNA degradation on agarose gels have been detected in six strains of Streptomyces. All the enzymes were located in the cell wall-cytoplasmic membrane space, and released after protoplast production. Synthesis of these nucleases was dependent on the composition of the growth media. Differentiation on agar plates was affected by the same nutritional conditions that regulate DNAse production. All DNases were deoxyriboendonucleases that required Mg2+ and a low ionic concentration for optimal activity. The molecular masses of native DNases range from 37 +/- 2 to 43 +/- 4 kDa. The enzymes produced nicks in double-stranded DNA and were unable to digest RNA. The widespread presence, location and characteristics of such nucleases in Streptomyces suggest a common role for these enzymes.