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  • Title: A radical on the Met-Tyr-Trp modification required for catalase activity in catalase-peroxidase is established by isotopic labeling and site-directed mutagenesis.
    Author: Zhao X, Suarez J, Khajo A, Yu S, Metlitsky L, Magliozzo RS.
    Journal: J Am Chem Soc; 2010 Jun 23; 132(24):8268-9. PubMed ID: 20507091.
    Abstract:
    A transient tyrosyl-like radical with a narrow doublet X-band EPR signal is present during catalase turnover by Mycobacterium tuberculosis catalase-peroxidase (KatG). Labeling of KatG with beta-methylene-deuterated tyrosine causes a collapse of the doublet to a singlet, while for 3,5-ring-deuterated tyrosine-labeled enzyme, no changes occur in the EPR signal. Except for the replacement Tyr229Phe, all other single-tyrosine mutants of KatG exhibit the same narrow doublet EPR signal and catalase activity similar to that of the wild-type enzyme. These findings confirm that this catalytically competent radical is associated with Tyr229, whose 3' and 5' protons are replaced as a result of cross-links with neighboring Met255 and Trp107 side chains in the post-translationally modified enzyme containing a distal-side Met255-Tyr229-Trp107 adduct.
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