title: Binding and modification of proteins by methylglyoxal under physiological conditions. A kinetic and mechanistic study with N alpha-acetylarginine, N alpha-acetylcysteine, and N alpha-acetyllysine, and bovine serum albumin.
abstract: The physiological alpha-oxoaldehyde methylglyoxal binds and modifies arginine, lysine, and cysteine residues in proteins. The kinetics and mechanism of these reactions were investigated with N alpha-acetylamino acids and bovine serum albumin at pH 7.4 and 37 degrees C. The reaction of methylglyoxal with N alpha-acetylarginine involved the initial reversible formation of glycosylamine and 4,5-dihydroxy-5-methylimidazolidine derivatives, with further slow irreversible conversion to an imidazolone, N alpha-acetyl-N delta- (5-methyl-4-imidazolon-2-yl)ornithine. The imidazolone was fluorescent with an excitation lambda max value of 320 nm and an emission lambda max value of 398 nm. Methylglyoxal reacted reversibly with N alpha-acetyllysine to form glycosylamine and bisglycosylamine derivatives. Further reaction of these glycosylamines occurred to form brown, fluorescent oligomers that were not characterized. Methylglyoxal reacted rapidly and reversibly with N alpha-acetylcysteine to form the hemithioacetal adduct. The reaction of methylglyoxal with bovine serum albumin (BSA) at pH 7.4 and 37 degrees C involved the reversible and irreversible formation of methylglyoxal-BSA adducts. Irreversible modification of BSA occurred mainly on arginine residues to form imidazolone. The formation of methylglyoxal-modified proteins involves glycoxidation leading to advanced glycation end product-like fluorescence. It is expected to be increased in diabetes mellitus and may be linked to the development of diabetic complications.
authors.affiliation: Department of Chemistry and Biological Chemistry, University of Essex, Colchester, United Kingdom.
authors.forename: T W
authors.initials: TW
authors.lastname: Lo
authors.forename: M E
authors.initials: ME
authors.lastname: Westwood
authors.forename: A C
authors.initials: AC
authors.lastname: McLellan
authors.forename: T
authors.initials: T
authors.lastname: Selwood
authors.forename: P J
authors.initials: PJ
authors.lastname: Thornalley
mesh_terms: D000111:Acetylcysteine / Q000737:chemistry / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011765:Pyruvaldehyde / Q000737:chemistry / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism*
chemical_list: C002315:N(alpha)-acetyllysine; D012710:Serum Albumin, Bovine; D011765:Pyruvaldehyde; D001120:Arginine; D008239:Lysine; C000015:N-acetyl-L-arginine; D000111:Acetylcysteine