In order to generate inhibition constants, we used the assumption that acetyl-CoA going to acyl-enzyme intermediate is very fast compared to decarboxylative Claisen condensation. As such our inhibitors compete with malonyl-CoA binding. In the UV-Vis assays we did not find inhibition by acetyl-oxa(dethia)CoA and unexpectedly, we noticed a couple percent activation. This suggests acetyl-oxa(dethia)CoA somewhat mimics acetyl-CoA as far as promoting FabH activation. The activation seen in the full UV-Vis assay suggests a dual role for acetyloxa(dethia)CoA, since there was some inhibition seen for FabH decarboxylation of malonyl-CoA to acetoacetyl-CoA. Inhibition by acetyl-aza(dethia)CoA is moderately stronger than substrate binding, Ki of 800 µM, see With product analogs in hand, we explored their ability to inhibit the reaction, again based on an assumption they competed for malonyl-CoA binding. We found that CoA is a reasonable inhibitor with a Ki of 0.15 mM, while, oxa(dethia)CoA inhibits with a Ki of 0.4 mM and aza(dethia)CoA inhibits with a Ki of 0.9 mM.