The Decomposition of Yeast Nucleic Acid by a Heat Resistant Enzyme.

The yeast nucleic acid used in these experiments was a commercial preparation purified by treatment with picric acid (3). A sample of yeast nucleic acid and one of thymus nucleic acid were kindly supplied by Dr. P. A. Levene to whom the author wishes to extend his heartiest thanks. The effect of the enzyme preparations on nucleic acid was followed by determining the amount of total phosphorus rendered soluble in hydrochloric acid during the incubation of the enzymesubstrate mixture. To this end, the mixture was treated with HCl (final conoentration 0.2 ~)j and then immediately cooled and centrifuged in the cold. The supernatant was then analyzed for phosphorus by the Youngburg and Youngburg method (4) modified in details. It was found necessary to prolong the digestion with sulfuric acid for 40 minutes in order to obtain a complete liberation of the phosphorus in the inorganic form. MacFadyen followed the decomposition of nucleic acid by deter-