Directional regulation of cytosolic PEPCK catalysis is mediated by competitive binding of anions

• Published in: Biochemical and biophysical research communications 2022-12, Vol.637, p.218-223
• Main Authors: Barwell, Sarah A.E., Duman, Ramona, Wagner, Armin, Holyoak, Todd
• Format: Article
• Language: English
• Subjects: Anions; Binding, Competitive; carboxy-lyases; Catalysis; catalytic activity; chlorides; enzyme activity; enzyme inhibition; gluconeogenesis; glucose; oxaloacetic acid; Phosphoenolpyruvate; Phosphoenolpyruvate Carboxykinase (ATP)
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2022.11.025

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. •Cytosolic PEPCK generates PEP from OAA in its role as an essential cataplerotic enzyme in primary metabolism.•In vitro this interconversion is freely reversible.•Specific binding of anions such as chloride asymmetrically inhibit PEPCK consistent with its unidirectional metabolic role.