Peroxidases electron transfer rate constants

Similarly, this amphiphilic polymer micelle was also used to dismpt the complex between cytochrome c (Cc) and cytochrome c peroxidase (CcP Sandanaraj, Bayraktar et al. 2007). In this case, we found that the polymer modulates the redox properties of the protein upon binding. The polymer binding exposes the heme cofactor of the protein, which is buried in the protein and alters the coordination environment of the metal. The exposure of heme was confirmed by UV-vis, CD spectroscopy, fluorescence spectroscopy, and electrochemical kinetic smdies. The rate constant of electron transfer (fc°) increased by 3 orders of magnimde for the protein-polymer complex compared to protein alone. To establish that the polymer micelle is capable of disrupting the Cc-CcP complex, the polymer micelle was added to the preformed Cc-CcP complex. The observed for this complex was the same as that of the Cc-polymer complex, which confirms that the polymer micelle is indeed capable of disrupting the Cc-CcP complex. 

Comparison of the rate constants of [(TMP)Fe =0] + and HRP compound I was further extended to reactions with a series of sulfides [108]. HRP is known to convert thioanisole to the corresponding sulfoxide [109], although peroxidases typically catalyze two sequential one-electron oxidations such as one-electron oxidation of phenol derivatives to phenoxy radicals [110], The yield of the sulfoxide from the stoichiometric reaction of HRP compound I with thioanisole is only 25 + 5 %. The sulfoxidation involves oxygen-transfer from an oxoferryl species to sulfide, because in H2 02 has been shown to be incorporated into the product sulfoxide [108, 111], The initial rapid conversion of compound I to compound II (fci) by thioanisole is followed by further reduction to the ferric resting state, as is found for reactions with DMA [108, 112, 113]. A linear correlation between log A i and E°ox for the reactions of HRP compound I with thioanisoles (Figure 2) is readily combined with the relationship for DMA (Figure la) into a single, common relationship (Eq. 8) [108]. 

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