Studies on the Specificity of an Acid Deoxyribonuclease from <em>Helix aspersa</em> (Müll.).

The kinetics of degradation of calf thymus DNA by the DNAase from Helix aspersa has been investigated in its middle and terminal phase by determining both hyperchromic shift and average chain length of the digest. The results obtained are practically identical with those previously reported for acid DNAase from hog spleen. In contrast, the distribution of the isostichs in snail DNAase digests is significantly different from those found for spleen acid DNAase digests of similar sizes. The 3′phosphate and 5′-hydroxy terminal nucleotides were found not to vary in their compositions in the average size range 34 to 10 and 70 to 12, respectively. In the 3′-phosphate terminal position, deoxyadenosine is by far predominant (78%) and deoxycytidine almost absent (less than 1%); deoxyguanosinc and thymidine form 6% and 16%, respectively, of the terminals. In the 5′-hydroxy terminal position deoxyguanosine is predominant (45%), followed by deoxycytidine (31%), thymidine (14%) and deoxyadenosine (10%); in the 5′-hydroxy penultimate position thymidine forms 38% of the nucleotides, deoxyguanosine 24%, deoxy-adenosine 21% and deoxycytidine 17%. [ABSTRACT FROM AUTHOR]