FIG. 5.

Effect of rabbit polyclonal antiserum on GTP activation and UTP inhibition. UMP kinase was incubated as described for Fig. 4A with a polyclonal antiserum solution calculated to yield 50% inhibition. This resulting activity (•), in the absence of GTP or UTP, was considered 100% in this set of experiments. Enzyme activity was then assayed with 1 mM ATP, 1 mM UMP, and various concentrations of GTP (A) or with 1 mM ATP, 0.1 mM UMP, and various concentrations of UTP (B). Results of control experiments in the absence of polyclonal antiserum (○) are also indicated.