ATP is the main source for energy. GTP is needed for activation of biochemical processes.
Cells synthesize purine nucleotides in two ways.
The other way of synthesis is utilization of ready made purine bases in the salvage pathway. Many purine nucleotide biosynthesis inhibitors are used therapeutically against cancer. Cancer cells divide faster than normal cells and thus require more purine nucleotides for DNA synthesis than normal cells. Disorders in the de novo purine nucleotide biosynthesis can cause gout. Except for viruses and certain parasites, all organisms can synthesize purine nucleotides de novo .