Identification of glyoxal and arabinose as intermediates in the autoxidative modification of proteins by glucose

KJ Wells-Knecht, DV Zyzak, JE Litchfield… - Biochemistry, 1995 - ACS Publications
KJ Wells-Knecht, DV Zyzak, JE Litchfield, SR Thorpe, JW Baynes
Biochemistry, 1995ACS Publications
Revised Manuscript Received December 12, 1994® abstract: Glycation and oxidation
reactions contribute to protein modification in agingand diabetes. Formation of dicarbonyl
sugars during autoxidation of glucose is the hypothetical first step in the autoxidative
glycosylation andsubsequent browning of proteins by glucose [Wolff, SP, & Dean, RT(1987)
Biochem. J. 245,243—250]. In order to identify the dicarbonyl sugar (s) formedduring
autoxidation of glucose underphysiological conditions, glucose was incubated in phosphate …
Revised Manuscript Received December 12, 1994® abstract: Glycation and oxidation reactions contribute to protein modification in agingand diabetes. Formation of dicarbonyl sugars during autoxidation of glucose is the hypothetical first step in the autoxidative glycosylation andsubsequent browning of proteins by glucose [Wolff, S. P., & Dean, R. T.(1987) Biochem. J. 245,243—250]. In order to identify the dicarbonyl sugar (s) formedduring autoxidation of glucose underphysiological conditions, glucose was incubated in phosphate buffer (pH 7.4) at 37 C under air (oxidative conditions) or nitrogen with transition metal chelators (antioxidative conditions). Dicarbonyl compounds were analyzed spectrophotometrically and by HPLC after reaction with Girard-T reagent. Carbohydrates were analyzed by gas chromatography—mass spectrometry. Both dicarbonyl sugar and arabinose concentrations increased with time and glucose concentration in incubations conducted under oxidative conditions; only trace amounts of these products were detected in glucose incubated under antioxidative conditions. HPLC analysis of adducts formed with Girard-T reagent indicated that glyoxal was the only-dicarbonyl sugar formed on autoxidation of glucose. Glyoxal and arabinose accounted for> 50% of the glucose lost during a 21 day incubation. Neither glucosone nor its degradation product, ribulose, was detectable. Reaction of glyoxal with RNase yielded the glycoxidation product, Nf-(carboxymethyl) lysine, while arabinose is a source of pentosidine. Our results implicate glyoxal and arabinose as intermediates in the browning and crosslinking of proteins by glucose under oxidative conditions. They also provide a mechanism by which antioxidants and dicarbonyl trapping reagents, such as aminoguanidine, limit glycoxidation reactions and support further evaluation of these types of compounds for inhibition of chemical modification and crosslinking of proteins during aging and diabetes.
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