Kinetics of dithionite reduction of the heme nonapeptide of cytochrome c.
The kinetics of dithionite reduction of the oxidized heme nonapeptide fragment of horse heart cytochrome c have been measured as a function of ionic strength at pH 7 and pH 9 by the stopped-flow technique. Dithionite concentration dependences indicate that the radical anion monomer, SO2-., is the active reductant. The pH 7 ionic strength dependence suggests that the heme peptide is reacting as a negatively charged molecule (its overall charge is calculated to be -1). Comparison of these results with the known rate of dithionite reduction of cytochrome c indicates that the heme nonapeptide has substantially greater inherent reactivity than cytochrome c, perhaps due to the greater accessibility of the heme.
Arif Kazmi
S
S
Mills
M A
MA
Pitluk
Z W
ZW
Scott
R A
RA
D000818:Animals; D003574:Cytochrome c Group / Q000378:metabolism*; D045304:Cytochromes c; D004227:Dithionite; D006418:Heme / Q000378:metabolism; D006736:Horses; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000378:metabolism*
D003574:Cytochrome c Group; D010446:Peptide Fragments; C046027:heme nonapeptide; D004227:Dithionite; D006418:Heme; D045304:Cytochromes c