Figure 1

APN/CD13 enzyme activity in HeLa cells with or without (control) of radiation (16 Gy). Enzyme activity was determined by quantitating the enzymatic cleavage of the synthetic substrate alanine-p-nitroanilido. After 1 hour incubation, APN/CD13 activity is depicted as about two fold increase in HeLa cells after radiation. Radiation increased APN/CD13 enzyme activity. Errors bar represent the standard error of the mean.