Identification of Covalent Catechin Adducts of Enoyl-ACP Reductase (FabI) from E. coli using Mass Spectrometry

Enoyl-ACP reductase (FabI), an enzyme which is inhibited by catechin, is essential for lipid biosynthesis in bacteria (E. coli). Another FabI inhibitor, triclosan, has strong antibacterial effects,1 but overuse can be detrimental to the environment. Flavonoids, a class of dietary compounds, are known to have potent inhibitory effects on FabI and other kinases.2,3,4 Adducts form as a result of the biochemical reaction between flavonoids and cysteine, a modification which can be verified by m/z shifts on the mass spectra.5 Samples of E. coli protein with overexpressed FabI are utilized: the wild type with ordinary primary structure, and mutant type lacking the cysteine residue proximate to the active site. Testing for a covalent bond with C210 is suitable for contributions to informatics pertaining to flavonoid-protein bioactivity. Confirmation of a covalent bond would be novel, demonstrating how flavonoids induce structural changes in bacterial protein. Understanding flavonoid interactions with bacteria is key to determining its role in the diet and influences on endogenous microbial communities.