A Radical on the Met-Tyr-Trp Modification Required for Catalase Activity in Catalase-Peroxidase Is Established by Isotopic Labeling and Site-Directed Mutagenesis

作者：Zhao Xiangbo; Suarez Javier; Khajo Abdelahad; Yu Shengwei; Metlitsky Leonid; Magliozzo Richard S^*

来源：Journal of the American Chemical Society, 2010, 132(24): 8268-+.

DOI：10.1021/ja103311e

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.

• 出版日期2010-6-23