It was thought until recently that fructosamines are not metabolized in mammalian cells. Quite to the contrary, a mammalian enzyme, fructosamine 3-kinase, has recently been identified, which phosphorylates fructosamines on their third carbon, making them unstable and leading to their shedding from proteins. Fructosamine 3-kinase is therefore responsible for protein deglycation, one of the few protein repair mechanisms that have been identified.
Van Schaftingen, E. (2004). Fructosamine 3-kinase et réparation des protéines. Academie Royale de Medecine de Belgique. Bulletin et Memoires, 159(1-2), 103-109. https://hdl.handle.net/2078.5/121359 (Original work published 2004)