Chloroperoxidase-catalyzed oxidation of 4,6-dimethyldibenzothiophene as dimer complexes: evidence for kinetic cooperativity.
A sigmoidal kinetic behavior of chloroperoxidase for the oxidation of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in water-miscible organic solvent is for the first time reported. Kinetics of 4,6-DMDBT oxidation showed a cooperative profile probably due to the capacity of chloroperoxidase to recognize a substrate dimer (pi-pi dimer) in its active site. Experimental evidence is given for dimer formation and its presence in the active site of chloroperoxidase. The kinetic data were adjusted for a binding site able to interact with either monomer or dimer substrates, producing a cooperative model describing a one-site binding of two related species. Determination of kinetics constants by iterative calculations of possible oxidation paths of 4,6-DMDBT suggests that kinetics oxidation of dimer substrate is preferred when compared to monomer oxidation. Steady-state fluorometry of substrate in the absence and presence of chloroperoxidase, described by the spectral center of mass, supports this last conclusion.
Torres
Eduardo
E
Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, 07730 Mexico City, Mexico.
Aburto
Jorge
J
D002384:Catalysis; D002711:Chloride Peroxidase / Q000378:metabolism*; D019281:Dimerization; D007700:Kinetics; D010084:Oxidation-Reduction; D013057:Spectrum Analysis; D013876:Thiophenes / Q000737:chemistry* / Q000378:metabolism*
C414426:4,6-dimethyldibenzothiophene; D013876:Thiophenes; D002711:Chloride Peroxidase