Enzymes of nucleic acid metabolism as biochemical markers of T cell development in mouse

The levels of three purine salvage enzymes, adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and 5'-nucleotidase (5'-N), which are known to be associated with certain immunodeficiency disorders were determined in mouse T lymphocytes. These enzymes showed characteristic changes depending on the stage of T cell development. The activity of ADA was 5-fold higher in thymocytes compared to splenic T cells. On the other hand, the splenic T cells displayed a 2-fold and a 4-8 fold greater activity of PNP and 5'-N, respectively than those of thymocytes. The apparent Km and Vmax values have been determined for all the 3 enzymes in the immature and mature T cells. The data demonstrate that the absolute and relative activity of these enzymes may be used as biochemical markers to characterize the T lymphocytes during different stages of differentiation.