Heme-copper oxidases (HCOs) catalyze the O2 reduction reaction to H2O and play an significant role in biology. To investigate the catalysis in a better controlled manner, an artificial metalloenzyme based on myoglobin, termed as Phe33Tyr-CuBMb, was synthesized to mimic the activity of HCOs. Moreover, experiments found that unnatural Tyr analogs and different heme substituents could affect the reactivity and selectivity of this artificial metalloenzyme. In addition, water has been proposed to play an important role in this enzymatic catalysis as well. However, the detailed understanding of these regulations has not been fully established. A recent study indicated that the proton transfer step ahead of the O-O cleavage is the rate-determining step of the catalysis by HCOs. Herein, by using theoretical methods, we investigate the fundamental mechanism of the proton-coupled electron transfer reaction (PCET), which is ahead of the O-O cleavage, in the catalysis by Phe33Tyr-CuBMb as well as the Tyr, heme, and water effects on this PCET reaction. Specifically, quantum mechanical (QM), molecular dynamics (MD), and quantum mechanical/molecular mechanical (QM/MM) methods have been employed in our study. Important insights have been obtained for these regulations and would be helpful for the further interpretation of the experimental results.

Theoretical study of the proton-coupled electron transfer reaction catalyzed by Phe33Tyr-CuBMb

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