HYDROLYSIS OF CALF THYMUS DEOXYRIBONUCLEATE BY PANCREATIC DEOXYRIBONUCLEASE: II. ISOLATION AND ANALYSIS OF THE MONONUCLEOTIDES AND DINUCLEOTIDES OBTAINED BY ENZYMIC DEGRADATION IN THE PRESENCE OF MANGANOUS IONS

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Abstract
Analysis of the oligonucleotides produced by the exhaustive hydrolysis of calf thymus DNA by pancreatic DNAase in the presence of manganous ions at pH 6.6 shows an increase in the concentration of mononucleotides and dinucleotides which are found to comprise 5% and 49% of the total nucleotide phosphorus. The relative amounts of the isomeric dinucleotides formed during manganous ion activation of the enzyme differ from those obtained for magnesium ion activation. The results are interpreted as indicating a random attack by the enzyme at multiple points in an endonuclease action with certain linkages being more susceptible than others. The evidence suggests that the pPu–pPu linkage is stable and that the increased liberation of purine nucleotides occupying the 5′-terminal phosphate position is due to hydrolysis of pPy–pPu linkages.