Publications

• Fructosamine 3-kinase is involved in an intracellular deglycation pathway in human erythrocytes.

  Delpierre G., Collard F., Fortpied J., Van Schaftingen E.

  Fructosamine 3-kinase, which phosphorylates low-molecular-mass and protein-bound fructosamines on the third carbon of their deoxyfructose moiety, is quite active in erythrocytes, and was proposed to initiate a process removing fructosamine residues from proteins. In the present study, we show that ... >> More

  Fructosamine 3-kinase, which phosphorylates low-molecular-mass and protein-bound fructosamines on the third carbon of their deoxyfructose moiety, is quite active in erythrocytes, and was proposed to initiate a process removing fructosamine residues from proteins. In the present study, we show that incubation of human erythrocytes with 200 mM glucose not only caused the progressive formation of glycated haemoglobin, but also increased the level of an anionic form of haemoglobin containing alkali-labile phosphate, to approx. 5% of total haemoglobin. 1-Deoxy-1-morpholinofructose (DMF), a substrate and competitive inhibitor of fructosamine 3-kinase, doubled the rate of accumulation of glycated haemoglobin, but markedly decreased the amount of haemoglobin containing alkali-labile phosphate. The latter corresponds therefore to haemoglobin bound to a fructosamine 3-phosphate group (FN3P-Hb). Returning erythrocytes incubated with 200 mM glucose and DMF to a low-glucose medium devoid of DMF caused a decrease in the amount of glycated haemoglobin, a transient increase in FN3P-Hb and a net decrease in the sum (glycated haemoglobin+FN3P-Hb). These effects were prevented by DMF, indicating that fructosamine 3-kinase is involved in the removal of fructosamine residues. The second step of this 'deglycation' process is most likely a spontaneous decomposition of the fructosamine 3-phosphate residues to a free amine, 3-deoxyglucosone and P(i). This is consistent with the findings that 2-oxo-3-deoxygluconate, the product of 3-deoxyglucosone oxidation, is formed in erythrocytes incubated for 2 days with 200 mM glucose in a sufficient amount to account for the removal of fructosamine residues from proteins, and that DMF appears to inhibit the formation of 2-oxo-3-deoxygluconate from elevated glucose concentrations. << Less

  Biochem. J. 365:801-808(2002) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Human fructosamine-3-kinase: purification, sequencing, substrate specificity, and evidence of activity in vivo.

  Szwergold B.S., Howell S., Beisswenger P.J.

  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- ... >> More

  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). << Less

  Diabetes 50:2139-2147(2001) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Identification, cloning, and heterologous expression of a mammalian fructosamine-3-kinase.

  Delpierre G., Rider M.H., Collard F., Stroobant V., Vanstapel F., Santos H., Van Schaftingen E.

  Fructosamines are thought to play an important role in the development of diabetic complications. Little is known about reactions that could metabolize these compounds in mammalian tissues, except for recent indications that they can be converted to fructosamine 3-phosphates. The purpose of the pr ... >> More

  Fructosamines are thought to play an important role in the development of diabetic complications. Little is known about reactions that could metabolize these compounds in mammalian tissues, except for recent indications that they can be converted to fructosamine 3-phosphates. The purpose of the present work was to identify and characterize the enzyme responsible for this conversion. Erythrocyte extracts were found to catalyze the ATP-dependent phosphorylation of 1-deoxy-1-morpholinofructose (DMF), a synthetic fructosamine. The enzyme responsible for this conversion was purified approximately 2,500-fold by chromatography on Blue Sepharose, Q Sepharose, and Sephacryl S-200 and shown to copurify with a 35,000-M(r) protein. Partial sequences of tryptic peptides were derived from the protein by nanoelectrospray-ionization mass spectrometry, which allowed for the identification of the corresponding human and mouse cDNAs. Both cDNAs encode proteins of 309 amino acids, showing 89% identity with each other and homologous to proteins of unknown function predicted from the sequences of several bacterial genomes. Both proteins were expressed in Escherichia coli and purified. They were shown to catalyze the phosphorylation of DMF, fructoselysine, fructoseglycine, and fructose in order of decreasing affinity. They also phosphorylated glycated lysozyme, though not unmodified lysozyme. Nuclear magnetic resonance analysis of phosphorylated DMF and phosphorylated fructoseglycine showed that the phosphate was bound to the third carbon of the 1-deoxyfructose moiety. The physiological function of fructosamine-3-kinase may be to initiate a process leading to the deglycation of fructoselysine and of glycated proteins. << Less

  Diabetes 49:1627-1634(2000) [PubMed] [EuropePMC]