La Dégradation Enzymatique de L'Acide Désoxyribonucléique. IV.‐Mise au Point et Application D'Une Méthode D'Adsorption

Abstract

Calf thymus deoxyribonucleic acid (DNA) was hydrolyzed by pancreas and by spleen deoxyribonucleases (DNases I and 11). The hydrolysates were adsorbed on Ecteola cellulose and eluted by successive amounts of 0.1, 0.2 and 0.3 M NaC1. Oligonucleotides of increasing sizes were present in the eluates and were determined spectroscopically. This provided a simple method for following the whole course of the enzymic hydrolysis. Moreover it was possible to estimate the percentage and the average degree of polymerization of the oligonucleotides produced.The enzymic action of DNase I was studied in varied conditions of temperature and in the presence of several activating cations. It was confirmed that there were two phases : a rapid one mostly activated by Mg ions and by Mn2+ and Co2+, a slow one activated by Ca2+. The highest rate was obtained with mixtures of Mg2+ and Ca2+. These results were interpreted by supposing the existence of a second enzyme in the DNase preparation, an oligonucleotidase.With DNase 11, higher oligonucleotides were produced. Native DNA, DNA denatured by heat or by desionization and DNA degraded by ultrasonic waves were submitted to the action of both DNases. Their behaviour was very similar. It seems that the intact structure of native DNA is not an important requirement for the enzymic action.