Catabolism of thymidine during the lymphocyte cell cycle.

Concanavalin A-stimulated lymphocytes degrade thymidine to beta-aminoisobutyric acid. Thymidine-catabolizing enzymes are active in the cells during G1, G2 and mitosis, but activity falls to very low levels just prior to the onset of S and remains low throughout the S period. The data suggest that cell pools of thymidine are regulated by degradation.