Characterizing lysine acetylation of Escherichia coli type II citrate synthase

The citrate synthase (CS) catalyzes the first reaction of the tricarboxylic acid cycle, playing an important role in central metabolism. The acetylation of lysine residues in the Escherichia coli Type II CS has been identified at multiple sites by proteomic studies, but their effects remain unknown. In this study, we applied the genetic code expansion strategy to generate 10 site-specifically acetylated CS variants which have been identified in nature. Enzyme assays and kinetic analyses showed that lysine acetylation could decrease the overall CS enzyme activity, largely due to the acetylation of K295 which impaired the binding of acetyl-coenzyme A. Further genetic studies as well as in vitro acetylation and deacetylation assays were performed to explore the acetylation and deacetylation processes of the CS, which indicated that the CS could be acetylated by acetyl-phosphate chemically, and be deacetylated by the CobB deacetylase.