PAFAH1B2 encodes the alpha2 catalytic subunit of cytosolic platelet-activating factor acetylhydrolase 1b (PAF-AH Ib), which hydrolyzes the acetyl group at the sn-2 position of PAF and related phospholipids 1. The enzyme functions as part of a heterotetrameric complex with regulatory and catalytic subunits, where different subunit compositions affect substrate specificity 1. PAFAH1B2 plays a critical role in aspirin metabolism, as it represents the major aspirin hydrolase in human erythrocytes, with activity varying 3-fold among individuals and correlating with PAFAH1B2 levels 12. The enzyme also functions extracellularly in plasma as a homomeric form, contributing to aspirin hydrolysis alongside butyrylcholinesterase 2. In cancer contexts, PAFAH1B2 is overexpressed in pancreatic ductal adenocarcinoma as a HIF1α target gene, promoting epithelial-mesenchymal transition, migration, invasion, and metastasis 3. In breast cancer, cathepsin G induces PAFAH1B2 expression, leading to enhanced PAF degradation and suppressed PAF receptor signaling, which promotes malignant cell migration and aggregation 4. Alternative splicing produces testis-specific isoforms with altered catalytic properties 5.