PAPSS1 encodes a bifunctional enzyme critical for sulfate metabolism, catalyzing the synthesis of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), the universal sulfate donor for all sulfotransferase reactions 1. The enzyme contains two functional domains: an N-terminal APS kinase domain and a C-terminal ATP sulfurylase domain, which sequentially convert inorganic sulfate and ATP first to adenosine 5'-phosphosulfate (APS), then to PAPS 1. PAPSS1 is predominantly expressed in brain and skin tissues, distinguishing it from PAPSS2 which predominates in liver and cartilage 1. The gene shows significant genetic variation, with polymorphisms like Arg333Cys (2.5% frequency in Caucasians) and Glu531Gln affecting substrate kinetic properties, particularly altering sulfate binding affinity 2. In cancer contexts, PAPSS1 demonstrates complex roles: it acts as a tumor suppressor in esophageal squamous cell carcinoma where high expression correlates with better survival 3, while in ovarian cancer, PAPSS1 downregulation sensitizes cells to cisplatin by modulating estrogen receptor α signaling 4. Recent studies identify PAPSS1 as a potential therapeutic target, with synthetic lethality observed when PAPSS2 is co-deleted with PTEN 5, making it an attractive target for precision cancer therapy.