Phosphoenolpyruvate carboxykinase (PEPCK) plays a crucial role in gluconeogenesis. In this work, we analyze the proteolysis of Arabidopsis thaliana PEPCK1 (AthPEPCK1) in germinating seedlings. We found that expression of AthPEPCK1 peaks at 24-48 hours post-imbibition. Concomitantly, we observed shorter versions of AthPEPCK1, putatively generated by metacaspase-9 (AthMC9). To study the impact of AthMC9 cleavage on the kinetic and regulatory properties of AthPEPCK1, we produced truncated mutants based on the reported AthMC9 cleavage sites. The Δ19 and Δ101 truncated mutants of AthPEPCK1 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 of AthPEPCK1 in germinating seedlings operates as a mechanism to adapt the sensitivity to allosteric regulation during the sink-to-source transition.

中文翻译：

---

拟南芥磷酸烯醇丙酮酸羧化激酶1的蛋白水解切割改变其变构调节。

磷酸烯醇丙酮酸羧激酶（PEPCK）在糖异生中起关键作用。在这项工作中，我们分析了拟南芥PEPCK1（AthPEPCK1）在发芽幼苗中的蛋白水解。我们发现AthPEPCK1的表达在吸收后24-48小时达到峰值。同时，我们观察到了由metacaspase-9（AthMC9）生成的较短版本的AthPEPCK1。为了研究AthMC9裂解对AthPEPCK1动力学和调控特性的影响，我们根据报道的AthMC9裂解位点生产了截短的突变体。与WT相比，AthPEPCK1的Δ19和Δ101截短突变体显示出相似的动力学参数和相同的四级结构。然而，在Δ101突变体中废除了苹果酸的活化和6-磷酸葡萄糖的抑制。