Author (Your Name)

Amy Shedd, Colby College

Date of Award

1990

Document Type

Senior Scholars Paper (Colby Access Only)

Department

Colby College. Chemistry Dept.

Advisor(s)

R. Daniel Libby

Abstract

Chloroperoxidase is a heme enzyme known to catalyze halide dependent reactions, although the mechanism for these reactions is a source of controversy. The substrates 2,4,6-trimethylphenol and catechol behave competitively In the chloroperoxidase catalyzed halogen dependent reactions. It is not clear, however, whether the substrates are competing for an enzymatic halogen intermediate or for a free halogen intermediate. Hypochlorite has been proposed as a possible free halogen intermediate. Spectrophotometric studies show that the ratio of trimethylphenol product to catechol product in the enzyme system is about 1: 1. The same studies performed in a model HOCI system, in the absence of enzyme, show that trimethylphenol is favored more than catechol, confirming that the two systems are not exactly alike. The same relative reactivities were observed when the studies were repeated with bromine instead of chlorine. The trimethylphenol and catechol competition data as well as data collected with the substrate, 2-chlorodimedone, support the hypothesis that the reaction is occurring both partially with the free halogen intermediate and with an enzymatic halogenating intermediate.

Keywords

Chloroperoxidase, enzyme, 2, 4, 6-trimethylphenol, halogenation, bromination, chlorination

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