Probing Variable Axial Ligation in Nickel Superoxide Dismutase Utilizing Metallopeptide Based Models: Insight into the Superoxide Disproportionation Mechanism
Nickel superoxide dismutase (NiSOD) is a bacterial metalloenzyme that possesses a mononuclear Ni-center and catalyzes the disproportionation of O2*- by cycling between NiII and NiIII oxidation states. Herein we present evidence from several SOD active metallopeptide maquettes ([Ni(SODM2H(1)X)]; SODM2H(1)X = H2N-XCDLPCG-COOH; X = H, D, or A) that the Ni-center of NiSOD most likely remains five-coordinate during SOD catalysis using thin-film voltammetry. N3- and CN- titration studies suggest that O2*- disproportionation by [Ni(SODM2H(1)X)] proceeds via an outersphere mechanism. Computationally derived values for the nuclear reorganization energy of the [NiII(SODM2)]/[NiIII(SODM2)] self-exchange reaction combined with the experimentally determined value for ko (450 s-1) suggest that axial ligation enhances the O2*- disproportionation reaction in [Ni(SODM2)] (and NiSOD by analogy) by optimizing the NiII/NiIII redox couple such that it is close to the midpoint of the O2*- reduction and oxidation couples.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959766
- Report Number(s):
- BNL-82752-2009-JA; JACSAT; TRN: US201016%%910
- Journal Information:
- Journal of the American Chemical Society, Vol. 129; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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