FN3K encodes fructosamine-3-kinase, a metabolic kinase that catalyzes protein deglycation by phosphorylating fructoselysine residues on glycated proteins, generating unstable fructoselysine-3-phosphate adducts that decompose under physiological conditions. This deglycation activity is particularly important in erythrocytes and protects against accumulation of advanced glycation end-products (AGEs). FN3K also mediates deglycation of the transcription factor NRF2, which regulates cellular stress responses; glycation impairs NRF2 function and its binding to cofactors. Interindividual variability in FN3K activity is substantial and genetically determined by polymorphisms in the FN3K gene 1, with some evidence that lower activity correlates with increased site-specific hemoglobin glycation 1. FN3K has emerged as a therapeutic target in cancer: the oncogenic activity of NRF2 depends on FN3K-mediated deglycation, and hepatocellular carcinoma development triggered by MYC and Keap1 inactivation requires FN3K in vivo 2. In breast cancer, anticancer drugs including gefitinib, sorafenib, neratinib, and oxaliplatin modulate FN3K expression and NRF2-driven antioxidant signaling 3. Additionally, FN3K shows potential therapeutic utility in AGE-related cataracts, where ex vivo and in vivo FN3K treatment reduced AGE-related autofluorescence in lens tissues 4.