NT5C3B encodes 5'-nucleotidase, cytosolic IIIB, a specialized enzyme that specifically hydrolyzes 7-methylguanosine monophosphate (m7GMP) to 7-methylguanosine and inorganic phosphate 12. This specific activity likely protects cells against unwanted salvage of m7GMP and its incorporation into nucleic acids 1. The enzyme also exhibits weak activity toward CMP, while UMP and purine nucleotides are poor substrates 12. NT5C3B participates in mRNA catabolic processes, specifically deadenylation-dependent decay pathways, and localizes to the cytosol and cytoplasm. Genetically, NT5C3B variants show associations with multiple complex traits: a SNP (rs4796712) associated with airway wall thickness in smokers showed increased lung tissue expression with the risk allele 3. Gene-environment interaction analyses identified NT5C3B interactions with BMI for blood pressure phenotypes 4. In disease contexts, NT5C3B showed altered methylation in coal-burning arsenic poisoning populations 5 and was identified as a gene expression biomarker in pediatric acute lymphoblastic leukemia diagnostics 6. NT5C3B was also associated with fold-change in plasma amyloid-β42 levels in African Americans 7. These findings suggest NT5C3B's involvement in lung function, metabolic phenotypes, and potential disease biomarkers.