FN3K (fructosamine 3-kinase) is a mammalian enzyme that catalyses the phosphorylation of fructosamines, which thereby becomes unstable and detaches from proteins. The homologous mammalian enzyme, FN3K-RP (FN3K-related protein), does not phosphorylate fructosamines but ribulosamines, which are probably formed through a spontaneous reaction of amines with ribose 5-phosphate, an intermediate of the pentose–phosphate pathway and the Calvin cycle. We show in the present study that spinach leaf extracts display a substantial ribulosamine kinase activity (approx. 700 times higher than the specific activity of FN3K in erythrocytes). The ribulosamine kinase was purified approx. 400 times and shown to phosphorylate ribulose-ε-lysine, protein-bound ribulosamines and also, with higher affinity, erythrulose-ε-lysine and protein-bound erythrulosamines. Evidence is presented for the fact that the third carbon of the sugar portion is phosphorylated by this enzyme and that this leads to the formation of unstable compounds decomposing with half-lives of approx. 30 min at 37 °C (ribulosamine 3-phosphates) and 5 min at 30 °C (erythrulosamine 3-phosphates). This decomposition results in the formation of a 2-oxo-3-deoxyaldose and inorganic phosphate, with regeneration of the free amino group. The Arabidopsis thaliana homologue of FN3K/FN3K-RP was overexpressed in Escherichia coli and shown to have properties similar to those of the enzyme purified from spinach leaves. These results indicate that the plant FN3K/FN3K-RP homologue, which appears to be targeted to the chloroplast in many species, is a ribulosamine/erythrulosamine 3-kinase. This enzyme may participate in a protein deglycation process removing Amadori products derived from ribose 5-phosphate and erythrose 4-phosphate, two Calvin cycle intermediates that are potent glycating agents.
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Research Article|
June 07 2005
Plant ribulosamine/erythrulosamine 3-kinase, a putative protein-repair enzyme
Juliette FORTPIED;
Juliette FORTPIED
*Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology and Université Catholique de Louvain, Avenue Hippocrate 75, B-1200 Brussels, Belgium
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Rita GEMAYEL;
Rita GEMAYEL
*Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology and Université Catholique de Louvain, Avenue Hippocrate 75, B-1200 Brussels, Belgium
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Vincent STROOBANT;
Vincent STROOBANT
†Ludwig Institute for Cancer Research, Avenue Hippocrate 74, B-1200 Brussels, Belgium
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Emile van SCHAFTINGEN
Emile van SCHAFTINGEN
1
*Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology and Université Catholique de Louvain, Avenue Hippocrate 75, B-1200 Brussels, Belgium
1To whom correspondence should be addressed (email vanschaftingen@bchm.ucl.ac.be).
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Publisher: Portland Press Ltd
Received:
November 29 2004
Revision Received:
February 08 2005
Accepted:
February 11 2005
Accepted Manuscript online:
February 11 2005
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2005
Biochem J (2005) 388 (3): 795–802.
Article history
Received:
November 29 2004
Revision Received:
February 08 2005
Accepted:
February 11 2005
Accepted Manuscript online:
February 11 2005
Citation
Juliette FORTPIED, Rita GEMAYEL, Vincent STROOBANT, Emile van SCHAFTINGEN; Plant ribulosamine/erythrulosamine 3-kinase, a putative protein-repair enzyme. Biochem J 15 June 2005; 388 (3): 795–802. doi: https://doi.org/10.1042/BJ20041976
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