FUT5 is an alpha(1,3)-fucosyltransferase that catalyzes the transfer of L-fucose from GDP-beta-L-fucose to N-acetyl-beta-D-glucosamine residues on glycoproteins and glycolipids 1. The enzyme preferentially fucosylates type 2 oligosaccharide chains via alpha(1,3) linkages and, to a lesser extent, type 1 chains via alpha(1,4) linkages, generating Lewis X/SSEA-1 and sialyl Lewis X antigens 1. FUT5 is encoded on chromosome 19 and shares >85% sequence homology with related fucosyltransferases FUT3 and FUT6 2. In cancer biology, FUT5 promotes colorectal cancer cell proliferation, migration, and invasion through the PI3K-Akt signaling pathway; miR-125a-3p negatively regulates FUT5 expression to suppress these oncogenic functions 3. Similarly, FUT5 down-regulation in gastric cancer reduces sialyl-Lewis antigen expression and diminishes cell adhesion to endothelial cells via E-selectin binding and hyaluronic acid interaction 4. Beyond cancer, FUT5 functions as a receptor for glycodelin-A on human sperm, where it acts as a zona pellucida protein receptor; glycodelin-A binding to sperm FUT5 inhibits spermatozoa-zona pellucida binding, suggesting a role in fertilization regulation 5. Recent Mendelian randomization analysis identified FUT5 as a potential cerebrospinal fluid biomarker and therapeutic target for endometriosis 6.