Modeling the O2 and NO reduction activity of heme/Cu oxidases

INOR 940

Simona C. Puiu, spuiu1@jhu.edu, Eduardo E Chufán, echufan@jhu.edu, Biplab Mondal, biplab@jhu.edu, and Kenneth D. Karlin, karlin@jhu.edu. Department of Chemistry, The Johns Hopkins University, 3400 North Charles St., Baltimore, MD 21218
Cytochrome c oxidase (CcO) is the enzyme that catalyzes the 4e-/4H+ reduction of molecular oxygen to water, at an active site consisting of a heme a3/CuB center. Nitric oxide can also bind to CcO and heme/copper oxidases are able to catalyze the reduction of NO to N2O, like the related nitric oxide reductase (NOR). The mechanisms of O2 and NO reduction share common features, but they are not completely understood. We present two approaches to effect the O-O cleavage, which rely on the reaction of iron-peroxo heme a3 synthetic model complexes with CuB analogues, in the presence of external proton sources and/or electron donors. These reactions yield a product assigned as an oxo-ferryl (FeIV=O) species (at -80oC) as proven by low-temperature UV-Vis studies and indirectly by its ability to oxidize phosphines. We also present preliminary studies of NO interaction with both reduced (heme Fe2+-Cu+) and mixed-valence (heme Fe3+-Cu+) complexes.
 

Bioinorganic Modeling
1:30 PM-5:30 PM, Wednesday, 13 September 2006 Moscone Center -- Room 307, Oral

Division of Inorganic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006