Critical roles of glutamine as nitrogen donors in purine and pyrimidine nucleotide synthesis: asparaginase treatment in childhood acute lymphoblastic leukemia.

Asparaginase is a key component of the chemotherapy protocols used in the treatment of acute lymphoblastic leukemia (ALL). The current treatment protocols are remarkable in that childhood ALL cure rates are approaching 85%. As the name implies, asparaginase catalyzes the deamination of asparagine to aspartic acid. What is not generally realized is that asparaginase also catalyzes, essentially to the same extent, the removal of the amide nitrogen from glutamine to form glutamic acid. Glutamine is a required substrate for three enzymes involved in the de novo synthesis of purine nucleotides and two enzymes involved in the de novo synthesis of pyrimidine nucleotides. In this review, the specific roles of glutamine in the de novo synthesis of nucleotides are defined and an appropriate explanation for the cell cycle arrest and cytotoxicity induced in proliferating malignant lymphoblasts by asparaginase treatment is provided.