Exonucleolytic Degradation of High Molecular Weight Deoxyribonucleic Acid and Ribonucleic Acid to Nucleoside 3'-Phosphates by a Nuclease from Bacillus subtilis

Abstract

Abstract A Ca++-dependent extracellular nuclease which degrades high molecular weight native and denatured deoxyribonucleic acid and ribonucleic acid completely to nucleoside 3'-monophosphates has been partially purified from culture fluids of Bacillus subtilis. The enzyme is easily prepared and completely stable to storage for over a year. Degradation of DNA and RNA is predominantly exonucleolytic. The approximate ratio of exo- to endonucleolytic scissions by the enzyme of native phage λ DNA is 2 x 104, of single stranded circular M13 phage DNA it is 103, and of 23 S Escherichia coli ribosomal RNA it is 102. Hydrolysis of oligoribonucleotides terminated with a 3'-phosphate group occurs from the 3' end. Hydrolysis of oligoribonucleotides lacking a 3'-phosphate is 5- to 20-fold slower and is not exclusively from either the 3' or the 5' end. Denatured DNA appears to be degraded from the 5' end of the chain but a simultaneous attack from the 3' terminus cannot be excluded.