Ketosamine-3-kinase, also known as FN3KRP, catalyzes the phosphorylation of psicosamines and ribulosamines compared to the neighboring gene which encodes a highly similar enzyme, fructosamine-3-kinase, which has different substrate specificity. The activity of both enzymes may result in deglycation of proteins to restore their function. Recombinant human FN3KRP protein, fused to His-tag at N-terminus, was expressed in E.coli.