Formation and detection of oxidant-generated tryptophan dimers in peptides and proteins.

In this study, second-order rate constants were determined for Trp(●) dimerization in Trp-containing peptides to be 2-6 × 10(8)M(-1) s(-1) by pulse radiolysis. Peptide charge and molecular mass correlated negatively with these rate constants. Exposure of Trp-containing peptides to steady-state radiolysis in the presence of NaN3 resulted in consumption of the parent peptide, and detection by LC-MS of up to 4 different isomeric Trp-Trp cross-links. Similar species were detected with other oxidants, including CO3(●-) (from the HCO3(-) -dependent peroxidase activity of bovine superoxide dismutase) and peroxynitrous acid (ONOOH) in the presence or absence of HCO3(-). Trp-Trp species were also isolated and detected after alkaline hydrolysis of the oxidized peptides and proteins. These studies demonstrate that Trp(●) formed on peptides and proteins undergo rapid recombination reactions to form Trp-Trp cross-linked species. These products may serve as markers of radical-mediated protein damage, and represent an additional pathway to protein aggregation in cellular dysfunction and disease. PMID: 28962874 [PubMed - as supplied by publisher]
Source: Free Radical Biology and Medicine - Category: Biology Authors: Tags: Free Radic Biol Med Source Type: research