PAPSS2 (3'-phosphoadenosine 5'-phosphosulfate synthase 2) is a bifunctional enzyme catalyzing two sequential steps in sulfate activation, first converting ATP and inorganic sulfate to adenosine 5'-phosphosulfate (APS), then phosphorylating APS to generate 3'-phosphoadenosine 5'-phosphosulfate (PAPS) 1. PAPS serves as the universal sulfate donor for all sulfotransferase-catalyzed conjugation reactions in mammals 2. PAPSS2 localizes to both the cytosol and nucleus, with expression regulated by transcription factors including the aryl hydrocarbon receptor and hypoxia-responsive pathways 34. Clinically, PAPSS2 plays critical roles in intestinal homeostasis and hepatic protection. Loss-of-function mutations cause brachyolmia type 4, characterized by skeletal dysplasia and androgen excess 5. Intestinal-specific PAPSS2 knockout increases susceptibility to colitis and colonic carcinogenesis by reducing mucin sulfation and increasing intestinal permeability 6. Conversely, enhancing intestinal PAPSS2 expression via dietary indole-3-acetic acid supplementation protects against colitis 3. In hepatocytes, PAPSS2 inhibition paradoxically confers protection against acetaminophen-induced liver failure by preventing p53 sulfation and activating antioxidant responses 7. Additionally, elevated PAPSS2 expression correlates with longevity in humans 8 and facilitates hepatocellular carcinoma adaptation to hypoxia through histone sulfation 4. These diverse functions highlight PAPSS2 as a therapeutic target for inflammatory bowel disease, liver injury, and cancer.