Markers of protein oxidation: different oxidants give rise to variable yields of bound and released carbonyl products.
Exposure of proteins to radicals in the presence of O2 gives both side-chain oxidation and backbone fragmentation. These processes can be interrelated, with initial side-chain oxidation giving rise to backbone damage via transfer reactions. We have shown previously that alkoxyl radicals formed on the C-3 carbons of Ala, Val, Leu, and Asp residues undergo beta-scission to give backbone alpha-carbon radicals, with the release of the side- chain as a carbonyl compound. We now show that this is a general mechanism that occurs with a wide range of oxidants. The quantitative significance of this process depends on the extent of oxidation at C-3 compared with other sites. HO*, generated by gamma radiolysis, gave the highest total carbonyl yield, with protein-bound carbonyls predominating over released. In contrast, metal ion/H2O2 systems, gave more released than bound carbonyls, with this ratio modulated by EDTA. This is ascribed to metal ion-protein interactions affecting the sites of initial oxidation. Hypochlorous acid gave low concentrations of released carbonyls, but high yields of protein-bound material. The peroxyl radical generator 2,2'-azobis(2-amidinopropane) hydrochloride, and a peroxynitrite generator, 3-morpholinosydnonimine hydrochloride, gave lower overall carbonyl yields, with released carbonyls predominating over protein-bound species similar to that observed with metal ion/H2O2 systems.
Headlam
Henrietta A
HA
Free Radical Group, Heart Research Institute, Camperdown, Sydney, Australia.
Davies
Michael J
MJ
D000096:Acetone / Q000032:analysis / Q000737:chemistry; D000447:Aldehydes / Q000032:analysis / Q000737:chemistry; D005557:Formaldehyde / Q000032:analysis / Q000737:chemistry; D006038:Glyoxylates / Q000032:analysis / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry / Q000494:pharmacology*; D010084:Oxidation-Reduction; D011506:Proteins / Q000032:analysis / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000032:analysis / Q000737:chemistry
D000447:Aldehydes; D006038:Glyoxylates; D008670:Metals; D016877:Oxidants; D011506:Proteins; D000096:Acetone; D005557:Formaldehyde; D012710:Serum Albumin, Bovine; D006861:Hydrogen Peroxide; C017439:isobutyraldehyde; C031150:glyoxylic acid