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.
Liochev
Stefan I
SI
The Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Fridovich
Irwin
I
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