Initiates a process leading to the deglycation of proteins (PubMed:15705060). Phosphorylates low-molecular-mass and protein-bound erythrulosamines and ribulosamines, but not fructosamines or psicosamines, on the third carbon of the sugar moiety (PubMed:15705060). Protein-bound erythrulosamine 3-phosphates and ribulosamine 3-phosphates are unstable and decompose under physiological conditions (PubMed:15705060). ATP + N(6)-D-ribulosyl-L-lysyl-[protein] = ADP + H(+) + N(6)-(3-O-phospho-D-ribulosyl)-L-lysyl-[protein] ATP + N(6)-(D-erythrulosyl)-L-lysyl-[protein] = ADP + H(+) + N(6)-(3-O-phospho-D-erythrulosyl)-L-lysyl-[protein] Belongs to the fructosamine kinase family.