ARSJ (arylsulfatase family member J) is a sulfatase enzyme located on chromosome 4 that catalyzes the hydrolysis of sulfate ester bonds from biological substrates 1. As a member of the 17-member human sulfatase family, ARSJ contains the evolutionarily conserved active site that undergoes post-translational modification to C(alpha)-formylglycine (FGly), which is essential for catalytic activity 1. The enzyme localizes to the endoplasmic reticulum lumen and is involved in sulfuric ester hydrolase activity 2. During embryonic development, ARSJ demonstrates novel expression patterns specifically in developing joints 3. Clinically, ARSJ expression is significantly associated with colorectal cancer (CRC) overall survival, emerging as one of five key genes in predictive models for CRC prognosis 4. Additionally, ARSJ methylation status shows differential patterns in high-altitude polycythemia patients compared to healthy controls, with methylation differences reaching up to 78.1%, suggesting potential diagnostic relevance 5. ARSJ is also regulated by TGF-β signaling through miR-181b-5p in triple-negative breast cancer, linking it to oncogenic pathways 6. While the specific substrates and complete biological functions of ARSJ remain incompletely characterized, its expression patterns in developmental and pathological contexts indicate roles beyond basic cellular homeostasis.