Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
Diamond Light Source Ltd., Didcot, OX11 0DE, UK.
Biochem Biophys Res Commun. 2022 Dec 31;637:218-223. doi: 10.1016/j.bbrc.2022.11.025. Epub 2022 Nov 11.
Phosphoenolpyruvate carboxykinase (PEPCK) is a well-characterized enzyme involved in primary glucose metabolism, responsible for catalyzing one of the key steps of gluconeogenesis. It is well demonstrated that PEPCK can efficiently catalyze the reversible interconversion of oxaloacetic acid (OAA) to phosphoenolpyruvate (PEP) in vitro, but the enzyme is typically ascribed a metabolic role that requires preferential catalysis in the direction of PEP synthesis in vivo. Here we present structural and functional data that demonstrate the preferential synthesis of PEP from OAA catalyzed by PEPCK in vivo is facilitated by anion-mediated enzyme inhibition that reduces enzyme activity more significantly in the direction of OAA synthesis than in the direction of PEP synthesis. From our studies we conclude that the specific binding of small, ubiquitous anions like chloride, present in millimolar concentrations under normal cellular conditions allows for metabolic control by restricting PEPCK to function in the direction of PEP synthesis.
磷酸烯醇式丙酮酸羧激酶（PEPCK）是一种参与初级糖代谢的特征酶，负责催化糖异生的关键步骤之一。已有充分证据表明，PEPCK 能够在体外有效地催化草酰乙酸（OAA）与磷酸烯醇式丙酮酸（PEP）之间的可逆互变，但该酶通常被认为具有代谢作用，需要在体内优先催化 PEP 的合成。在这里，我们呈现了结构和功能数据，证明了阴离子介导的酶抑制促进了体内 OAA 优先合成 PEP，与 OAA 合成方向相比，这种抑制使酶活性在 PEP 合成方向上降低更为显著。通过我们的研究，我们得出结论，在正常细胞条件下以毫摩尔浓度存在的小而普遍存在的阴离子（如氯离子）的特异性结合，通过限制 PEPCK 只能在 PEP 合成方向上发挥作用，从而实现代谢控制。
