Misty M. Witt

Publication Date

1996

Document Type

Dissertation/Thesis

First Advisor

Erman, James E.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Chemistry

LCSH

Cytochrome oxidase; Potassium cyanide; Peroxidase

Abstract

The reactivity of potassium cyanide with a mutant of cytochrome c peroxidase in which the conserved distal histidine (His-52) was replaced with leucine [CcP(H52L)] was studied from pH 4 to 8 at 0.1 M ionic strength. Spectral studies were conducted to determine the coordination state of the heme in CcP(H52L) and in the CcP(H52L)/cyanide complex. Kinetic studies were performed to characterize the binding of cyanide to the enzyme as a function of pH. Based on the results of the study, it is suggested that HCN binds to the neutral pentacoordinate form of CcP(H52L). The association rate constant was found to be pH dependent while the dissociation rate constant was essentially independent of pH. The pH dependence of the association rate constant can be accounted for by a mechanism in which HCN can bind to either the neutral form or the hydroxy-ligated form of CcP(H52L). The iron-bound hydroxide assumes the role of base catalyst in CcP(H52L) just as His-52 does in native CcP. The dissociation rate constant for the CcP(H52L)/cyanide complex is about three times smaller than that for the native CcP/cyanide complex; this indicates slower dissociation of the ligand and suggests that His-52 may have a destabilizing effect on the bound cyanide by providing a proton to allow HCN to dissociate.

Comments

Includes bibliographical references (pages [93]-94)

Extent

viii, 111 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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