Formation of o-tyrosine and dityrosine in proteins during radiolytic and metal-catalyzed oxidation.
To evaluate their usefulness as chemical indicators of cumulative oxidative damage to proteins, we studied the kinetics and extent of formation of ortho-tyrosine (o-Tyr), dityrosine (DT), and dityrosine-like fluorescence (Ex = 317 nm, Em = 407 nm) in the model proteins RNase and lysozyme exposed to radiolytic and metal-catalyzed (H2O2/Cu2+) oxidation (MCO). Although there were protein-dependent differences, o-Tyr, DT, and fluorescence increased coordinately during oxidation of the proteins in both oxidation systems. The contribution of DT to total dityrosine-like fluorescence in oxidized proteins varied from 2-100%, depending on the protein, type of oxidation, and extent of oxidative damage. In proteins exposed to MCO, DT typically accounted for > 50% of the fluorescence at DT wavelengths. These studies indicate that o-Tyr and DT should be useful chemical markers of cumulative exposure of proteins to MCO in vitro and in vivo.
Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208.
T G
TG
Huggins
M C
MC
Wells-Knecht
N A
NA
Detorie
J W
JW
Baynes
S R
SR
Thorpe
D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007536:Isomerism; D007700:Kinetics; D009113:Muramidase / Q000737:chemistry / Q000187:drug effects / Q000528:radiation effects; D010084:Oxidation-Reduction; D011506:Proteins / Q000737:chemistry* / Q000187:drug effects / Q000528:radiation effects; D012260:Ribonucleases / Q000737:chemistry / Q000187:drug effects / Q000528:radiation effects; D014443:Tyrosine / Q000031:analogs & derivatives*
D011506:Proteins; D014443:Tyrosine; C026741:2-tyrosine; D006861:Hydrogen Peroxide; C007543:dityrosine; D012260:Ribonucleases; D009113:Muramidase