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Gene Review

FN3K  -  fructosamine 3 kinase

Homo sapiens

Synonyms: Fructosamine-3-kinase
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Disease relevance of FN3K

  • The genes were expressed in all human tissues examined, with FN3K showing significantly higher levels in organs susceptible to nonenzymatic glycation and diabetic complications [1].
  • Intrinsic toxicity of glucose, due to non-enzymatic glycation, is controlled in-vivo by deglycation systems including: FN3K-mediated deglycation of fructosamines and transglycation of aldosamines [2].
  • In this perspective, small changes in flow rates in the spermine (where ODC and antizyme are key players) and/or FN-3-K pathway could contribute to enhance the effects of hyperglycemia and explain why there are diabetic subjects with higher glycation phenotypes and incidence of complications [3].

High impact information on FN3K

  • Fructosamine-3-kinase (FN3K) is a recently described protein-repair enzyme responsible for the removal of fructosamines, which are the products of a spontaneous reaction of glucose with amines [4].
  • Fructosamine 6-phosphates, which result from the reaction of amines with Glu-6-P, were not substrates for FN3K [4].
  • The aim of this work was to identify the fructosamine residues on hemoglobin that are removed as a result of the action of FN3K in intact erythrocytes [5].
  • In this report, we describe the purification and characterization of a mammalian fructosamine-3-kinase (FN3K), which phosphorylates fructoselysine (FL) residues on glycated proteins, to FL-3-phosphate (FL3P) [6].
  • Because the condensation of glucose and lysine residues is an ubiquitous and unavoidable process in homeothermic organisms, a deglycation system mediated by FN3K may be an important factor in protecting cells from the deleterious effects of nonenzymatic glycation [6].

Biological context of FN3K


Anatomical context of FN3K

  • Cultured fibroblasts treated with conditions mimicking the hormonal and biochemical profile of the diabetic state showed no changes in FN3K and FN3KRP expression relative to untreated cells [1].
  • Moreover, analysis of the fructoselysine 3-phosphate content of haemoglobin from diabetic subjects suggests that, in addition to FN3K, another deglycating mechanism may be operative in human erythrocytes [11].
  • (4) Knockdown of FN3K in cultured cells inhibits or arrests their growth [7].

Associations of FN3K with chemical compounds

  • These include, among others, the fact that while the apparent deglycation mechanism does not operate on L-glucose, semi-purified FN3K appears to be able to use both D- and L-fructosamines as substrates [11].
  • NMR analysis indicated that 1-deoxy-1-morpholinopsicose (DMP, a substrate for FN3K and FN3K-RP), like 1-deoxy-1-morpholinofructose (DMF, a substrate of FN3K), penetrated erythrocytes and was converted into the corresponding 3-phospho-derivative [8].
  • We postulate that this, FN3K-independent, deglycation occurs by transglycation, in which carbohydrate moieties of glycated amines, such as glucoselysines on proteins, are removed by intracellular nucleophiles including free amino acids and peptides such as glutathione, carnosine and anserine [2].
  • Spermine and FN-3-K may be part of a carbonyl damage control pathway [3].
  • We have purified and characterized Amadorase, a fructosamine-3-kinase, and demonstrated both in vitro and in vivo that it is responsible for the production of 3-deoxyglucosone (3DG) [12].

Other interactions of FN3K

  • These data suggest that FN3K and FN3KRP act as protein repair enzymes and are expressed constitutively in human cells independently of some of the variables altered in the diabetic state [1].


  1. The expression of the genes for fructosamine-3-kinase and fructosamine-3-kinase-related protein appears to be constitutive and unaffected by environmental signals. Conner, J.R., Beisswenger, P.J., Szwergold, B.S. Biochem. Biophys. Res. Commun. (2004) [Pubmed]
  2. Intrinsic toxicity of glucose, due to non-enzymatic glycation, is controlled in-vivo by deglycation systems including: FN3K-mediated deglycation of fructosamines and transglycation of aldosamines. Szwergold, B.S. Med. Hypotheses (2005) [Pubmed]
  3. Alternative antiglycation mechanisms: are spermine and fructosamine-3-kinase part of a carbonyl damage control pathway? Gugliucci, A. Med. Hypotheses (2005) [Pubmed]
  4. Magnesium-dependent phosphatase-1 is a protein-fructosamine-6-phosphatase potentially involved in glycation repair. Fortpied, J., Maliekal, P., Vertommen, D., Van Schaftingen, E. J. Biol. Chem. (2006) [Pubmed]
  5. Identification of fructosamine residues deglycated by fructosamine-3-kinase in human hemoglobin. Delpierrre, G., Vertommen, D., Communi, D., Rider, M.H., Van Schaftingen, E. J. Biol. Chem. (2004) [Pubmed]
  6. Human fructosamine-3-kinase: purification, sequencing, substrate specificity, and evidence of activity in vivo. Szwergold, B.S., Howell, S., Beisswenger, P.J. Diabetes (2001) [Pubmed]
  7. Some clues as to the regulation, expression, function, and distribution of fructosamine-3-kinase and fructosamine-3-kinase-related protein. Conner, J.R., Beisswenger, P.J., Szwergold, B.S. Ann. N. Y. Acad. Sci. (2005) [Pubmed]
  8. Fructosamine 3-kinase-related protein and deglycation in human erythrocytes. Collard, F., Wiame, E., Bergans, N., Fortpied, J., Vertommen, D., Vanstapel, F., Delpierre, G., Van Schaftingen, E. Biochem. J. (2004) [Pubmed]
  9. Variability in erythrocyte fructosamine 3-kinase activity in humans correlates with polymorphisms in the FN3K gene and impacts on haemoglobin glycation at specific sites. Delpierre, G., Veiga-da-Cunha, M., Vertommen, D., Buysschaert, M., Van Schaftingen, E. Diabetes Metab. (2006) [Pubmed]
  10. Fructosamine 3-kinase, an enzyme involved in protein deglycation. Delpierre, G., Van Schaftingen, E. Biochem. Soc. Trans. (2003) [Pubmed]
  11. Enzymatic deglycation--a new paradigm or an epiphenomenon? Szwergold, B.S., Beisswenger, P.J. Biochem. Soc. Trans. (2003) [Pubmed]
  12. DYN 12, a small molecule inhibitor of the enzyme amadorase, lowers plasma 3-deoxyglucosone levels in diabetic rats. Kappler, F., Schwartz, M.L., Su, B., Tobia, A.M., Brown, T. Diabetes Technol. Ther. (2001) [Pubmed]
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