Kinetics of Pseudomonas aeruginosa cytochrome c551 and cytochrome oxidase oxidation by Co(phen)3(3+) and Mn(CyDTA)(H2O)-.
The reaction between reduced Pseudomonas cytochrome c551 and cytochrome oxidase with two inorganic metal complexes, Co(phen)3(3+) and Mn(CyDTA)(H2O)-, has been followed by stopped-flow spectrophotometry. The electron transfer to cytochrome c551 by both reactants is a simple process, characterized by the following second-order rate constant: k = 4.8 X 10(4) M-1 sec-1 in the case of Co(phen)3(3+) and k = 2.3 X 10(4) M-1 sec-1 in the case of Mn(CyDTA)(H2O)-. The reaction of the c-heme of the oxidase with both metal complexes is somewhat heterogeneous, the overall process being characterized by the following second-order rate constants: k = 1.7 X 10(3) M-1 sec-1 with Co(phen)3(3+) and k = 4.3 X 10(4) M-1 sec-1 with Mn(CyDTA)(H2O)- as oxidants; under CO (which binds to the d1-heme) the former constant increases by a factor of 2, while the latter does not change significantly. The oxidation of the d1-heme of the oxidase by Co(phen)3(3+) occurs via intramolecular electron transfer to the c-heme, a direct bimolecular transfer from the complex being operative only at high metal complex concentrations; when Mn(CyDTA)(H2O)- is the oxidant, the bimolecular oxidation of the d1-heme competes successfully with the intramolecular electron transfer.
Tordi
M G
MG
Department of Biochemical Sciences, University of Rome, La Sapienza, Italy.
Silvestrini
M C
MC
Adzamli
K
K
Brunori
M
M
D001426:Bacterial Proteins; D003574:Cytochrome c Group / Q000378:metabolism*; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D009942:Organometallic Compounds / Q000378:metabolism*; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000378:metabolism*
D001426:Bacterial Proteins; D003574:Cytochrome c Group; D009942:Organometallic Compounds; D010618:Phenanthrolines; C035551:triphenanthrolinecobalt(III); C053681:(1,2-diaminocyclohexane)-tetrakis(acetato)manganate; C017167:cytochrome C(551); D004492:Edetic Acid; D003576:Electron Transport Complex IV