APEX1 and infection: The following Arg × infection interaction was noted for APE-1 activity in the blood of turkeys (P = 0.009): C. perfringens infection decreased APE-1 activity at the lowest dietary Arg content (Arg90) and Met concentration of 45% Lys, but not at the medium or highest Arg content (Arg100 and Arg110, respectively) (Table 7).