Isolation of naturally occurring inhibitors of ribonucleotide reductase

Abstract

Ribonucleotide reductase activity was markedly inhibited by components isolated from Ehrlich ascites cells. These components were much more inhibitory to ribonucleotide reductase than to DNA polymerase from these cells. 14C-Thymidine incorporation studies showed that in general, there was a correlation between the degree of inhibition of reductase activity and the degree of inhibition of 14C-Thymidine incorporation into DNA of intact cells. Preliminary studies showed that this inhibitory fraction was also capable of retarding Ehrlich ascites tumor cell growth in mice.