Analysis of the interdependence of thioesterase specificity and FabF concentration. (A) Product distributions for modeled FASs (1 μM of each Fab, 10 μM thioesterase, 10 μM holo-ACP, 1 mM NADPH, 1 mM NADH, 0.5 mM malonyl-CoA, and 0.5 mM acetyl-CoA, 12.5 min) containing thioesterases specific for C4 (BfTES), C8 (CpFatB1), C12 (UcFatB), and C14 acyl-ACPs (TesA). (B) Total production by FASs from (A) with varying concentrations of FabF. FASs that contain thioesterases with narrow substrate specificities (e.g., CpFatB1 and UcFatB) show a pronounced sensitivity to FabF concentration. (C) Optimal concentrations of FabF increase with the length of thioesterase targets in both (i) the base model and (ii) a modified model that lacks inhibition of FabH by acyl-ACPs. The similarity in trends generated by these two models suggests that optimal FabF concentrations do not minimize inhibition but, rather, maximize the availability of acyl-ACPs targeted by thioesterases.