@article {CaltechAUTHORS_https://authors.library.caltech.edu/id/eprint/104465,
    title ="Does Tyrosine Protect S. Coelicolor Laccase from Oxidative Degradation?",
    author = "Kielb, Patrycja J. and Gray, Harry B.",
    
    
    
    
    month = "July",
    year = "2020",
    
    
    
    url = "https://resolver.caltech.edu/CaltechAUTHORS:20200720-145555975",
    note = "Licence: CC BY-NC-ND 4.0. \n\nSubmitted date: 18/07/2020; Posted date: 20/07/2020. \n\nFunding: National Institute of Diabetes and Digestive and Kidney Diseases. \n\nAuthors declare no conflict of interest.",
    revision_no = "12",
    abstract = "We have investigated the roles of tyrosine (Tyr) and tryptophan (Trp) residues in the four-electron reduction of oxygen catalyzed by Streptomyces coelicolor laccase (SLAC). During normal enzymatic turnover in laccases, reducing equivalents are delivered to a type 1 Cu center (Cu_(T1)) and then are transferred over 13 Å to a trinuclear Cu site (TNC: (Cu_(T3))₂Cu_(T2)) where O₂ reduction occurs. The TNC in SLAC is surrounded by a large cluster of Tyr and Trp residues that can provide reducing equivalents when the normal flow of electrons is disrupted. Canters and coworkers have shown that when O₂ reacts with a reduced SLAC variant lacking the CuT1 center, a Tyr108· radical near the TNC forms rapidly. We have found that ascorbate reduces the Tyr108· radical in wild-type SLAC about 10 times faster than it reacts with the Cu_(T1)²⁺ center, possibly owing to radical transfer along a Tyr/Trp chain. Aerobic oxidation of two reduced SLAC mutants (Y108F and W132F) leads to the formation of a long-lived (~15 min) Tyr· radical with distinct absorption at 408 nm. The diffusion of redox equivalents away from the primary enzymatic pathway in SLAC may indicate a poorly optimized enzyme or a mechanism to protect against protein damage.",
}