The 4-oxohexanoyl-ACP as an Alternate Acyl-Substrate for Pantoea stewartii EsaI AHL Synthase

Quorum sensing (QS) is cell-to-cell communication between bacteria facilitated by signal molecules called autoinducers which allows bacteria to activate gene expression contributing to increased virulence, biofilm formation, and antibiotic resistance. Pantoea stewartii causes Stewart’s wilt in corn through its QS mechanism. In P. stewartii , the substrates S-adenosyl-L-methionine (SAM) and 3-oxohexanoyl-acyl carrier protein (3-oxoC6-ACP) react in the active site of the enzyme EsaI to produce the autoinducer 3-oxohexanoyl-homoserine lactone (AHL). EsaI inhibitors could potentially mitigate pathogenic effects of P. stewartii . However, 3-oxoC6-ACP is difficult to synthesize, impeding EsaI characterization and inhibitor discovery for this enzyme. We have designed, synthesized and characterized 4-oxoC6-ACP as an alternate substrate for EsaI. The discovery of alternate substrates for 3-oxoAHL synthases such as EsaI should accelerate enzymological investigations and inhibitor development for this important class of enzymes.