| Autor: |
Reed JH, Shi Y; Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology , Hoboken, New Jersey 07030, United States., Zhu Q; Division of Environmental & Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States., Chakraborty S; Department of Chemistry & Biochemistry, University of Mississippi , Oxford, Mississippi 38677, United States., Mirts EN, Petrik ID, Bhagi-Damodaran A; Department of Pharmaceutical Chemistry, University of California, San Francisco , San Francisco, California 94143, United States., Ross M; Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States., Moënne-Loccoz P; Division of Environmental & Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , Portland, Oregon 97239, United States., Zhang Y; Department of Biomedical Engineering, Chemistry, and Biological Sciences, Stevens Institute of Technology , Hoboken, New Jersey 07030, United States., Lu Y |
| Abstrakt: |
The presence of a nonheme metal, such as copper and iron, in the heme-copper oxidase (HCO) superfamily is critical to the enzymatic activity of reducing O 2 to H 2 O, but the exact mechanism the nonheme metal ion uses to confer and fine-tune the activity remains to be understood. We herein report that manganese and cobalt can bind to the same nonheme site and confer HCO activity in a heme-nonheme biosynthetic model in myoglobin. While the initial rates of O 2 reduction by the Mn, Fe, and Co derivatives are similar, the percentages of reactive oxygen species (ROS) formation are 7%, 4%, and 1% and the total turnovers are 5.1 ± 1.1, 13.4 ± 0.7, and 82.5 ± 2.5, respectively. These results correlate with the trends of nonheme-metal-binding dissociation constants (35, 22, and 9 μM) closely, suggesting that tighter metal binding can prevent ROS release from the active site, lessen damage to the protein, and produce higher total turnover numbers. Detailed spectroscopic, electrochemical, and computational studies found no evidence of redox cycling of manganese or cobalt in the enzymatic reactions and suggest that structural and electronic effects related to the presence of different nonheme metals lead to the observed differences in reactivity. This study of the roles of nonheme metal ions beyond the Cu and Fe found in native enzymes has provided deeper insights into nature's choice of metal ion and reaction mechanism and allows for finer control of the enzymatic activity, which is a basis for the design of efficient catalysts for the oxygen reduction reaction in fuel cells. |
