Protein-fructosamine 3-kinase  Protein-fructosamine 3-kinase (, "FN3K", "fructosamine 3-kinase") is an enzyme with systematic name "ATP:(protein)-N6-D-fructosyl-L-lysine 3-phosphotransferase". This enzyme catalyses the following chemical reaction  Nonenzymatic glycation is a factor in the pathogenesis of diabetes.