Modulation of plant Acetyl CoA Synthetase activity by acetylation

Acetyl-CoA synthetase (ACS) is one of several enzymes that generate the key metabolic intermediate, acetyl-CoA. ACS in plant cells is part of a two-enzyme system that maintains acetate homeostasis, but its post-translational regulation is unknown. In microbes and mammals ACS activity is regulated by the post-translational acetylation of a key lysine residue that is positioned in a conserved domain near the carboxyl-end of the protein sequence. This study demonstrates that the plant ACS activity can be regulated by the acetylation of a specific lysine residue that is homologous to the regulatory lysine residue of microbial and mammalian ACS. The inhibitory effect of the acetylation of residue Lys-622 of the Arabidopsis ACS was demonstrated by site-directed mutagenesis, including the genetic substitution of this residue with the non-canonical N-{varepsilon}-acetyl-lysine residue. This latter modification lowered the catalytic efficiency of the enzyme by a factor of more than 500-fold. Michaelis-Menten kinetic analysis of the mutant enzyme indicates that this acetylation affects the first half-reaction of the ACS catalyzed reaction, namely the formation of the acetyl adenylate enzyme intermediate. The post-translational acetylation of the plant ACS would thus affect acetate flux in the plastids and overall acetate homeostasis. HighlightThe study demonstrates that acetylation of a specific lysine residue can regulate the activity of acetyl-CoA synthetase, a new regulatory mechanism for maintaining acetate homeostasis.