The function of FN3K (fructosamine 3 kinase, Ensembl gene identifier ENSG00000167363) is as follows. Fructosamine-3-kinase involved in protein deglycation by mediating phosphorylation of fructoselysine residues on glycated proteins, to generate fructoselysine-3 phosphate (PubMed:11016445, PubMed:11522682, PubMed:11975663). Fructoselysine-3 phosphate adducts are unstable and decompose under physiological conditions (PubMed:11522682, PubMed:11975663). Involved in intracellular deglycation in erythrocytes (PubMed:11975663). Involved in the response to oxidative stress by mediating deglycation of NFE2L2/NRF2, glycation impairing NFE2L2/NRF2 function (By similarity). Also able to phosphorylate psicosamines and ribulosamines (PubMed:14633848). {ECO:0000250|UniProtKB:Q9ER35, ECO:0000269|PubMed:11016445, ECO:0000269|PubMed:11522682, ECO:0000269|PubMed:11975663, ECO:0000269|PubMed:14633848}.