Interfacial Electrochemical Investigation of Dehaloperoxidase.

Abstract

The terebellid polychaete marine worm Amphitrite ornata contains an enzyme known as dehaloperoxidase (DHP). Dehaloperoxidase has unique characteristics that permit Amphitrite ornata to cohabit with other marine worms that secrete toxic haloaromatic compounds. Dehaloperoxidase has the capability to break down such compounds in the presence of hydrogen peroxide. For example, trihalophenols can be oxidized to dihaloquinones. Prior studies have described the structure, function, and mechanistic behavior of dehaloperoxidase. However, there have been no reports of the electrochemical analysis of dehaloperoxidase. The data in this thesis demonstrates the direct electrochemistry of dehaloperoxidase at bare indium tin oxide and at modified gold electrode surfaces. The gold electrodes were modified with HS(CH2)10COOH/HS(CH2)6OH mixed SAM. Not only diffusional voltammetry has been demonstrated, but also adsorption of electroactive dehaloperoxidase at the modified gold electrode surface. The successful electrochemistry of DHP is attributed to a cluster of lysines near a heme edge, analogous to cytochrome c. Using cyclic voltammetry, a formal reduction potential of the DHP FeIII/FeII heme couple in the presence of dioxygen was determined, which will provide insight into the enzymatic activity of the protein. This reduction potential was determined to be +440 mV v/s NHE. In the presence of tri-bromophenol, an organic substrate for DHP, the catalytic reduction was observed in the presence of dioxygen. In general, this thesis reports the first electrochemical investigation of dehaloperoxidase and explores its interfacial electrochemical properties at the indium tin oxide and modified gold electrode surfaces.