Proteolytic cleavage ofArabidopsis thalianaphosphoenolpyruvate carboxykinase-1 modifies its allosteric regulation

Abstract

AbstractPhosphoenolpyruvate carboxykinase (PEPCK) plays a crucial role in gluconeogenesis. In this work, we analyze the proteolysis ofArabidopsis thalianaPEPCK1 (AthPEPCK1) in germinating seedlings. We found that expression ofAthPEPCK1 peaks at 24-48 hours post-imbibition. Concomitantly, we observed shorter versions ofAthPEPCK1, putatively generated by metacaspase-9 (AthMC9). To study the impact ofAthMC9 cleavage on the kinetic and regulatory properties ofAthPEPCK1, we produced truncated mutants based on the reportedAthMC9 cleavage sites. The Δ19 and Δ101 truncated mutants ofAthPEPCK1 showed similar kinetic parameters and the same quaternary structure than the WT. However, activation by malate and inhibition by glucose 6-phosphate were abolished in the Δ101 mutant. We propose that proteolysis ofAthPEPCK1 in germinating seedlings operates as a mechanism to adapt the sensitivity to allosteric regulation during the sink-to-source transition.HighlightThis paper describes the effects of the N-terminal proteolytic cleavage on the kinetic and regulatory properties ofArabidopsis thalianaphosphoenolpyruvate carboxykinase-1.