Publication Date


Document Type


First Advisor

Erman, James E.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Chemistry


Cytochrome c; Peroxides; Peroxidase


The reaction of hydrogen peroxide and p-nitroperoxybenzoic acid with the enzyme cytochrome c peroxidase (CcP) was studied as a function of pH at 0.1M ionic strength. The purpose of these kinetic studies was to characterize the binding of neutral and negatively charged substrates to the enzyme. The reaction of hydrogen peroxide with CcP was studied from pH 4.0 to 11.0 and the apparent rate constant was found to be pH dependent. A mechanism was proposed assuming two ionizable groups on the enzyme influence the rate of the reaction. The enzyme was reactive when the group with pKa of 5.1 was unprotonated and the group with pKa of 10.4 was protonated. The true bimolecular rate constant at 0 .1M ionic strength was (3.5 ? 0.2) x 10^7 M^(-1)s^(-1). The reaction of p-nitroperoxybenzoic acid with CcP was studied from pH 4.5 to 7.0 at 0 .1M ionic strength. The reaction was found to be influenced by enzyme as well as substrate ionizations. A mechanism was proposed to explain the pH dependence. The pH range where the enzyme can rapidly react was lowered to 3.8 using non-nitrate buffers. The obtained bimolecular rates for the reaction of CcP with the neutral and the negatively charged forms of the substrate were found to be smaller than that with hydrogen peroxide.


Includes bibliographical references (pages [67]-69)


ix, 87 pages




Northern Illinois University

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