PEPCK (Phosphoenolpyruvate carboxykinase) is a key enzyme in gluconeogenesis, existing in two forms: PEPCK-C (cytosolic) and PEPCK-M (mitochondrial). It catalyzes the conversion of oxaloacetate to phosphoenolpyruvate, regulating blood glucose levels. PEPCK is primarily expressed in tissues such as the liver, kidney, and intestine, and its activity is regulated by various hormones including insulin and glucocorticoids. Variations in gene expression can affect gluconeogenesis rates and are associated with metabolic disorders such as diabetes and obesity. Mutations or alterations in PEPCK gene expression can lead to disturbances in energy metabolism, affecting metabolic homeostasis in organisms.