Fructosamine-3-kinase involved in protein deglycation by mediating phosphorylation of fructoselysine residues on glycated proteins, to generate fructoselysine-3 phosphate (PubMed:11016445, PubMed:16819943). Fructoselysine-3 phosphate adducts are unstable and decompose under physiological conditions (By similarity). Involved in intracellular deglycation in erythrocytes and pancreatic islets (PubMed:16819943, PubMed:20009024). Involved in the response to oxidative stress by mediating deglycation of NFE2L2/NRF2, glycation impairing NFE2L2/NRF2 function (PubMed:31398338). Also able to phosphorylate psicosamines and ribulosamines (By similarity). ATP + N(6)-(D-fructosyl)-L-lysyl-[protein] = ADP + H(+) + N(6)-(3-O-phospho-D-fructosyl)-L-lysyl-[protein] ATP + N(6)-D-ribulosyl-L-lysyl-[protein] = ADP + H(+) + N(6)-(3-O-phospho-D-ribulosyl)-L-lysyl-[protein] ATP + N(6)-(D-psicosyl)-L-lysyl-[protein] = ADP + H(+) + N(6)-(3-O-phospho-D-psicosyl)-L-lysyl-[protein] Monomer. Expressed in red blood cells, brain, heart, kidney and muscle (PubMed:15331600). Lower expression is observed in liver (PubMed:15331600). Not expressed in lung, spleen, testis and thymus (PubMed:15331600). Mice are viable and healthy and show normal blood glucose and serum fructosamine levels (PubMed:16819943). They however display increased protein glycation levels in cells such as erythrocytes and pancreatic islets (PubMed:16819943, PubMed:20009024). Increased levels of protein glycation levels do not affect the maintenance and function of pancreatic islets (PubMed:20009024). Belongs to the fructosamine kinase family.