Human Fructosamine-3-Kinase Purification, Sequencing, Substrate Specificity, and Evidence of Activity In Vivo

Department of Medicine, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Diabetes (Impact Factor: 8.1). 10/2001; 50(9):2139-47. DOI: 10.2337/diabetes.50.9.2139
Source: PubMed


Nonenzymatic glycation appears to be an important factor in the pathogenesis of diabetic complications. Key early intermediates in this process are fructosamines, such as protein-bound fructoselysines. 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). This phosphorylation destabilizes the FL adduct and leads to its spontaneous decomposition, thereby reversing the nonenzymatic glycation process at an early stage. FN3K was purified to homogeneity from human erythrocytes and sequenced by means of electrospray tandem mass spectrometry. The protein thus identified is a 35-kDa monomer that appears to be expressed in all mammalian tissues. It has no significant homology to other known proteins and appears to be encoded by genomic sequences located on human chromosomes 1 and 17. The lability of FL3P, the high affinity of FN3K for FL, and the wide distribution of FN3K suggest that the function of this enzyme is deglycation of nonenzymatically glycated proteins. 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. Our sequence data of FN3K are in excellent agreement with a recent report on this enzyme by Delpierre et al. (Diabetes 49:1627-1634, 2000).

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Available from: Benjamin. S. Szwergold, Aug 30, 2015
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    • "The enzymes do not act on fructosamines, but exclusively on the respective C3 epimers (psicosamines, ribulosamines and erythrulosamines); the resulting ketoamine 3-phosphate is unstable and decomposes spontaneously. The stability of these molecules at neutral pH is highly dependent on the size of their sugar moiety, and halflives of 8 h, 25 and <5 min have been observed for derivatives of hexoses, pentoses and tetroses, respectively (Szwergold et al. 2001; Collard et al. 2004; Fortpied et al. 2005). FN3K-RPs were discovered in several vertebrates such as fish and birds and also in plants (Collard et al. 2003; Fortpied et al. 2005; Delplanque et al. 2004; Gemayel et al. "
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    • "Another possibility to eliminate glycated proteins is by deglycating enzymes (the so-called amadoriases). Three types of enzymes able to deglycate proteins are known: fructoselysine oxidase (Takahashi et al., 1997), fructose- lysine-3-kinase (Szwergold et al., 2001) and fructosely- sine-6-kinase (Wiame et al., 2002). However, fructoselysine 3-kinase only has been detected in higher organisms. "
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