[Isolation of exonuclease A5 preparation free of phosphomonoesterase contamination].

A method is described of the isolation of exonuclease from cultural medium of Actinomyces sp. of coelicolor type, strain 5. The enzyme preparation is practically free from phosphatase activity (the ratio between exonuclease and phosphatase activities is about 10000). Chromatography on DEAE-Sephadex after the heating of the enzyme preparation at 37 degrees C and pH 5.5 in the presence of 2-mercaptoethanol was used to elimate the phosphatase contamination. The preparation of exonuclease A5 is suitable for different structural studies of nucleic acids, it can be used (instead of snake venom PDE) in a large scale preparation of 5'-mononucleotides from nucleic acids as well.