Biochemical Effects of Formycin, an Adenosine Analog1

The effects of formycin (7-amino-3-(/3-D-ribofuranosyl)pyrazolo(4,3-d)-pyrimidine), an adenosine analog, on purine metabolism in Ehrlich ascites tumor cells were studied. Purine biosynthesis de novo was blocked by formycin through inhibition of phosphoribosylpyrophosphate synthesis, and this did not occur in cells which did not phosphorylate formycin. This analog had no significant effect on adenine conversion to adenine and guanine nucleotides, but did inhibit the synthesis of these nucleotides from hypoxanthine and guanine. The incorporation of purines into nucleic acids was inhibited slightly. Formycin did not inhibit the phosphorolysis of guanosine or inosine, but did inhibit the incorporation of lysine and methionine into protein. For mycin 5'-phosphate inhibited adenine phosphoribosyltransferase