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. In microbial cells ACS generates the precursor for fatty acid and polyketide biosynthesis, and is regulated by the post-translational acetylation of a key lysine residue that inhibits catalytic activity. In contrast, ACS in plant cells is part of a two-enzyme system that maintains acetate homeostasis. Despite these different metabolic roles, this study demonstrates that the plant ACS can also be regulated by the acetylation of a specific lysine residue. The lysine residue that is targeted for this post translational modification reaction is positioned in a homologous region of the microbial and plant ACS sequences, occurring in the middle of a conserved motif. The inhibitory effect of the acetylation of residue Lys-622 of the Arabidopsis ACS was demonstrated by site-directed mutagenesis of this residue, including its genetic substitution with the non-canonical N-ε-acetyl-lysine residue. These modifications lowered the catalytic efficiency of the enzyme by a factor of more than 500-fold, and 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.
Circular dichroism, Secondary structure, Biochemistry