Use of a Metallopeptide-Based Mimic Provides Evidence for a Proton-Coupled Electron-Transfer Mechanism for Superoxide Reduction by Nickel-Containing Superoxide Dismutase

Authors


  • This work was supported by the National Science Foundation (CHE-0844234). X-ray absorption measurements were collected on X19a and X3b at the National Synchrotron Light Source (NSLS) which is funded by the DOE (contract no. DE-AC02-98CH10886). Work on X3b, which is part of the Case Center for Synchrotron Bioscience, was also supported by the NIH (P30-EB-009998). Profs. J. Mayer (Univ. of Washington), H. K. Shin (UNR), and an anonymous reviewer are acknowledged for valuable advice.

Abstract

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Sneaky little SOD! A metallopeptide-based mimic of nickel-containing superoxide dismutase was used to probe the mechanism of superoxide reduction by the metalloenzyme. Kinetic studies suggest a proton-coupled electron-transfer mechanism; large H/D kinetic isotope effects (KIE) are observed. XAS studies suggest the transferred H-atom is in the form of a NiII-S(H)-Cys moiety (see graph).

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