Amines, including those present on proteins, spontaneously react with glucose to make fructosamines in a reaction termed glycation. Fructosamine 3-kinase (FN3K), a 309-amino acid enzyme initially identified in erythrocytes, catalyzes the ATP-dependent phosphorylation of the third carbon on both D- and L-fructosamines, leading to their destabilization and eventually, their removal from the protein. FN3K is a monomer that is ubiquitously expressed in mammalian tissue and phosphorylates both low molecular mass and protein-bound fructosamines which are formed as a result of glycation of glucose with primary amines. FN3K protects proteins from the harmful effects of nonenzymatic glycation, and may also be involved in peptide repair and cell metabolism. FN3KRP (fructosamine-3-kinase-related protein) is a 309 amino acid protein that is expressed in erythrocytes, bone marrow, spleen, brain and kidney and belongs to the fructosamine kinase family. FN3KRP functions to phosphorylate psicoamines and ribulosamines on the third carbon of their sugar moiety, thereby leading to the deglycation of the target amines.
