DEPOLYMERIZING ENZYMES 19 



TABLE 9 



ENZYMIC DEGRADATION OF CALF THYMUS DEOXYRIBONUCLEIC ACID 



Abbreviations: A = adenine, G = guanine, T = thymine, C = cytosine, 

 Pu = purines, Py = pyrimidines. 



constituents to studies of enzymic reaction mechanisms for which 

 they are particularly suited. The action of crystalline deoxy- 

 ribonuclease on calf thymus deoxyribonucleic acid resulted in 

 the production of a large proportion of dialyzable fragments 

 (53% of the total after 6 hours digesdon), without liberarion of 

 ammonia or inorganic phosphate. But even after extended 

 digestion there remained a non-dialyzable core whose com- 

 position showed a significant divergence from both the original 

 nucleic acid and the bulk of the dialysate. The preliminary 

 findings summarized in Table 9 (Ref. 40) indicate a considerable 

 increase in the molar proportions of adenine to guanine and 

 especially to cytosine, of thymine to cytosine, and of purines to 

 pyrimidines. This shows that the dissymmetry in the distribution 

 of constituents, found in the original nucleic acid (Table 2), is 

 intensified in the core. The most plausible explanations of this 

 interesting phenomenon, the study of which is being continued, 

 are that the preparations consisted of more than one deoxy- 

 pentose nucleic acid or that the nucleic acid contained in its chain 

 clusters of nucleotides (relatively richer in adenine and thymine) 

 that were distinguished from the bulk of the molecule by greater 

 resistance to enzymic disintegration. 



In this connection another study, carried out in collaboration 

 with Zamenhof, should be mentioned briefly that dealt with the 



References p. 23 



