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.
Huggins
T G
TG
Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208.
Wells-Knecht
M C
MC
Detorie
N A
NA
Baynes
J W
JW
Thorpe
S R
SR
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