Human Fructosamine-3-Kinase Purification, Sequencing, Substrate Specificity, and Evidence of Activity In Vivo
ABSTRACT 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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ABSTRACT: Amadori products (fructosamines)-ubiquitously occurring in nature-are precursors of the toxic and cell damaging 'advanced glycation endproducts'; thus, it is not surprising that numerous organisms have developed systems to degrade such compounds. The deglycating enzymes differ with respect to their mechanisms as well as to their substrate specificities. Furthermore, different physiological functions are proposed for the different enzymes. The fructosamine 3-kinases of mammals and homologous proteins (fructosamine 3-kinase related proteins), which are common to all taxa, are thought to focus on intracellular repair functions. In contrast, in Bacillus subtilis and Escherichia coli, the cooperative action of a kinase and a deglycase facilitates Amadori degradation. As genes encoding these enzymes are co-transcribed with ABC transporter genes, it is thought that these genes facilitate the utilisation of extracellular Amadori products. Indeed, it has been shown that fructosamines can serve as the sole carbon and nitrogen sources. Here, we provide an overview of known deglycating systems with the emphasis on Amadori product degradation in bacteria.Applied Microbiology and Biotechnology 02/2011; 90(2):399-406. DOI:10.1007/s00253-010-3083-4 · 3.81 Impact Factor
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ABSTRACT: Advanced glycation end-products (AGEs) are formed from the so-called Amadori products by rearrangement followed by other reactions giving rise to compounds bound irreversibly. The structure of some of them is shown and the mechanism of formation is described. Several AGE binding molecules (Receptors for AGE, RAGE) are known and it is thought that many of the effects caused by AGEs are mediated by RAGE. Some of these were shown to be toxic, and called TAGE. The mechanism of detoxification of glyoxal and methylglyoxal by the glyoxalase system is described and also the possibility to eliminate glycated proteins by deglycation enzymes. Compounds able to inhibit AGEs formation are also taken into consideration.Amino Acids 07/2008; 35(1):29-36. DOI:10.1007/s00726-007-0606-0 · 3.65 Impact Factor
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ABSTRACT: Skin ageing is a complex biological process related to a decline in physiological and biochemical performance. A decline in the mitochondrial energy production is a feature of ageing at the cellular level. This is partially attributed to excessive production of reactive oxygen species such as superoxide and hydrogen peroxide in aged individuals. We have investigated the effect of (glyc)oxidative stress on two biochemical targets relevant for the energy metabolism of the skin. First, we showed an age dependent decline in the activity of the hydrogen peroxide detoxifying antioxidant catalase in stratum corneum on a chronically sun-exposed site. Furthermore catalase was sensitive to peroxynitrite-induced in vitro inactivation. Catalase mimetics as well as peroxynitrite scavengers are proposed to maintain hydrogen peroxide detoxification pathways. The second target was creatine kinase, an enzyme that controls the creatine-creatine phosphate shuttle. Creatine kinase lost activity after in vitro glycation by methylglyoxal. This activity loss could be prevented by antiglycation actives. These data suggest that biomolecules involved in energy homeostasis become damaged by different sources of stress. Actives specifically selected for optimal protection against these stress situations will decrease skin vulnerability and prevent the premature loss of skin function.Experimental Gerontology 10/2007; 42(9):924-9. DOI:10.1016/j.exger.2007.03.008 · 3.53 Impact Factor