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Understanding the Mechanism of Superoxide Reductase Promoted Reduction of Superoxide
Author(s) -
Brines Lisa M.,
Kovacs Julie A.
Publication year - 2007
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200600461
Subject(s) - chemistry , superoxide , hydrogen peroxide , active site , ferric , superoxide dismutase , protonation , catalysis , reactivity (psychology) , peroxide , catalytic cycle , stereochemistry , photochemistry , enzyme , biochemistry , organic chemistry , medicine , ion , alternative medicine , pathology
Superoxide reductases (SORs) are nonheme, iron‐containing enzymes which reduce superoxide (O 2 – ) to hydrogen peroxide (H 2 O 2 ) in anaerobic organisms. In contrast to the classical superoxide dismutases (SODs), SORs selectively reduce, rather than disproportionate, superoxide at an unusual [Fe(NHis) 4 SCys] catalytic site. Studies of the native enzyme and mutants have suggested the formation of a transient ferric‐(hydro)peroxide intermediate in SOR’s catalytic cycle, with subsequent protonation to yield hydrogen peroxide and a glutamate‐bound ferric resting state. With the synthesis of small molecular model compounds of the enzyme’s active site, analogous intermediates can be more thoroughly investigated in order to understand how the structure at the nonheme iron active site affects its function. Specific goals include the understanding of the role of the trans cysteinate in the promotion of SOR chemistry, as well as the role of the protons in the mechanism of the reaction. Because hydrogen peroxide formation requires two protons, investigation of the proton‐dependence of the formation of ferric‐(hydro)peroxo model complexes, as well as their subsequent reactivity with proton donors, yields important information about possible mechanisms. As new biochemical data on SORs become available, synthetic modeling, biophysical characterization, and DFT calculations continue to be important tools in the identification of viable mechanistic pathways.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)