An Extracellular Nuclease from Serratia marcescens

Abstract

An extracellular nuclease was isolated from Serratia marcescens culture fluid which rapidly hydrolyzed DNA and RNA at approximately the same rate. The activity of the enzyme was purified 2600-fold with a final recovery of 25%. The ratio of enzymatic activity with RNA as substrate to that with DNA as substrate remained approximately constant throughout the purification and in all studies of the properties of the enzyme, leading to the conclusion that both activities are associated with a single protein. The enzyme required Mg++ or Mn++ for activity, and had a pH optimum of 8.5. Heating the enzyme to 44° or higher reduced enzymatic activity; after 40 min at 44°, all activity was abolished. The nuclease could be stored in glass-sealed ampules at 4° for up to 3 months without loss of activity. These properties, in conjunction with the specificity reported in the accompanying paper, make this enzyme potentially useful as a reagent for the study of nucleic acid structure and function.