摘要：

The substance inducing transformation of pneumococcal types has been isolated from Pneumococcus Type III in the form of a desoxyribonucleic acid fraction (1). The data obtained by chemical, enzymatic, and serological analysis, as well as by electrophoresis and ultracentrifugation of the purified material strongly suggest that the nucleic acid is itself responsible for the biological activity. The enzymatic analysis was begun early in the course of the attempts to determine the nature of the transforming substance. Relatively unpurified pneumococcal extracts were subjected to enzymatic study in the hope that by this approach some clue might be obtained as to the identity of the biologically active constituent. Crystalline trypsin, chymotrypsin, and ribonuclease had no effect on the transforming substance, but it was found that certain crude enzyme preparations were able to bring about complete loss of transforming activity. When the possible importance of desoxyribonucleic acid was suggested by chemical fractionation, the experiments with crude enzyme preparations were extended to determine whether their ability to destroy the activity of the transforming principle could be correlated with any enzymatic action on authentic samples of desoxyribonucleic acid of non-bacterial origin. A variety of crude enzymes were tested both for their ability to inactivate the transforming substance, and for their effect on desoxyribonucleic acid from animal tissues (1). Of the enzyme preparations tested only those capable of depolymerizing authentic desoxyribonucleic acid were effective in destroying the transforming activity of pneumococcal extracts. Other parallelisms between the two actions were observed: for example, sodium fluoride inhibited both the depolymerizing action and the inactivation of the transforming sub-* The Bureau of Medicine and Surgery of the U. S. Navy does not necessarily undertake to endorse the views or opinions which are expressed in this paper.

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