In many bacterial pathogens, quorum sensing (QS) serves as an intercellular mechanism to regulate gene expression to establish pathogenic interactions with eukaryotic hosts or to colonize inanimate natural habitats. Disruption of quorum sensing is a promising strategy to attenuate pathogenicity without imposing the level of selective pressure associated with antibacterial treatments. In Gram-negative bacteria, acyl-homoserine lactone (acyl-HSL) signal molecules are synthesized by AHL synthase enzymes using acylated-acyl carrier protein (acyl-ACP) and S-adenosyl-L-methionine (SAM) as their substrates. Pantoea stewartii EsaI AHL synthase uses 3-oxo hexanoyl-ACP as the acyl-substrate to synthesize 3-oxo hexanoyl-HSL signal. Unfortunately, the instability of the β-ketoacyl-ACP substrate impedes mechanistic investigations for this class of enzymes. In this study, we systematically investigated the importance of β-keto moiety by varying hybridization at β-position, type of heteroatom, and position of the oxygen atom in the acyl-chain. Furanacetyl-ACP was identified as a good substrate for EsaI, with Km and kcat in agreement with native substrates of most studied AHL synthases today. Our efforts on developing alternative 3-oxo acyl-ACP substrates for EsaI should open new doors for investigating important anti-virulent drug targets such as LasI (Pseudomonas aeruginosa), YspI (Yersinia pestis), as well as other β-keto-acyl-ACP utilizing enzymes.

Investigation of catalytic activity of stable β-keto-acyl-ACP substrate analogs in quorum sensing signal synthesis

253rd National Meeting (2017)

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