Bicarbonate-enhanced peroxidase activity of Cu,Zn SOD: is the distal oxidant bound or diffusible?
The Cu,Zn SOD catalyzes the bicarbonate-dependent oxidation of a wide range of substrates by H2O2. A mechanism in accord with this activity has been described. It involves the generation of a strong oxidant (Cu(I)O, Cu(II)OH, or Cu(III)) by reaction of the active site Cu with H2O2, followed by oxidation of bicarbonate to CO3-* that in turn diffuses from the active site to oxidize the various substrates in free solution. Recently, an alternative mechanism, entailing firmly bound HCO3- and CO3-*, has been proposed [J. Biol. Chem. 278 (2003) 21032-21039]. We present data supporting the diffusible CO3-* and discuss the properties of this system that can be accommodated in this way and that preclude bound intermediates.
The Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Stefan I
SI
Liochev
Irwin
I
Fridovich
D001639:Bicarbonates / Q000378:metabolism*; D007700:Kinetics; D016877:Oxidants / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*; D013997:Time Factors
D001639:Bicarbonates; D016877:Oxidants; D009195:Peroxidase; D013482:Superoxide Dismutase