PFKL (phosphofructokinase, liver type) catalyzes the phosphorylation of D-fructose 6-phosphate to fructose 1,6-bisphosphate, the first committing step of glycolysis 1. Beyond its canonical glycolytic role, PFKL functions as a metabolic regulator with context-dependent functions. Mechanism: PFKL activity is dynamically regulated through phosphorylation at Ser775 during innate immune activation, increasing its catalytic activity and promoting glycolytic flux 2. During glucose deprivation, PFKL phosphorylation reduces its glycolytic activity but confers a moonlight protein kinase function, enabling PFKL to phosphorylate perilipin 2 (PLIN2) on lipid droplets and facilitate lipid droplet-mitochondria tethering to enhance fatty acid oxidation 3. Disease Relevance: PFKL expression is upregulated in hepatocellular carcinoma (HCC) and esophageal squamous cell carcinoma (ESCC), correlating with poor survival and advanced stages 45. PFKL also regulates vascular calcification through glycolysis-dependent histone lactylation pathways 6. Additionally, PFKL governs immune cell metabolism; selective PFKL activation suppresses the phagocytic oxidative burst in neutrophils by diverting glucose flux away from the pentose phosphate pathway 7. Clinical Significance: PFKL represents a therapeutic target in multiple cancers; EGR1-mediated transcriptional repression of PFKL suppresses HCC growth and enhances sorafenib sensitivity 4, while PFKL inhibition by penfluridol shows anti-cancer efficacy 5.