2Bach Institute of Biochemistry, Russian Academy of Sciences, Leninsky pr. 33, 119071 Moscow, Russia; fax: (495) 954-2732; E-mail: email@example.com
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Received April 17, 2008; Revision received September 6, 2008
The EPR signal recorded in reaction medium containing L-lysine and methylglyoxal is supposed to come from the anion radical (semidione) of methylglyoxal and cation radical of methylglyoxal dialkylimine. These free-radical intermediates might be formed as a result of electron transfer from dialkylimine to methylglyoxal. The EPR signal was observed in a nitrogen atmosphere, whereas only trace amounts of free radicals were registered under aerobic conditions. It has been established that the decay of methylglyoxal anion radical on aeration of the medium is inhibited by superoxide dismutase. Using the methods of EPR spectroscopy and lucigenin-dependent chemiluminescence, it has been shown that nonenzymatic generation of free radicals including superoxide anion radical takes place during the interaction of L-lysine with methylglyoxal – an intermediate of carbonyl stress – at different (including physiological) pH values. In the course of analogous reaction of L-lysine with malondialdehyde (the secondary product of the free radical derived oxidation of lipids), the formation of organic free radicals or superoxide radical was not observed.
KEY WORDS: free radicals, malondialdehyde, methylglyoxal, modification of amino acids