Determination of Km for adenylosuccinate (SAMP) in the absence or presence of several constant concentrations of adenosine phosphonobutyric acid, 2′(3′), 5′-diphosphate (APBADP) using WT B. subtilis ASL. The following APBADP concentrations are shown: 0 μM (◊), 0.25 μM (▴), 0.5 μM (□), 0.75 μM (▾), and 1.0 μM (○).