Studies on the Autolysis of Aspergillus oryzae Part XI

Abstract

Crystalline nuclease O obtained from autolyzed Aspergillus oryzae hydrolyzed heatdenatured calf thymus DNA 19 times faster than native DNA. Digestion of the heatdenatured DNA with an exess of the enzyme produced mono-, di- and tri-nucleotides with 5'-terminal phosphate, which amounted 3.4, 58.3 and 38.2%, respectively, of total degradation products. Hydrolysis of the native DNA with a sufficient amount of nuclease O produced mono-, di-, tri- and tetra-nucleotides with 5'-terminal phosphate, which amounted 1.9, 47.9, 36.7 and 13.6%, respectively, of total degradation products. Although nuclease O showed no strict base specificity on the native and heat-denatured DNA, diand tri-nucleotides in the digests were resistant to further hydrolysis by nuclease O. Native DNA was hydrolyzed by nuclease O through the mechanism of single strand break, which was shown by neutral and alkaline sucrose density gradient centrifugations.