Caldariomyces fumago Chloroperoxidase Catalyzes the Oxidative Dehalogenation of Chlorophenols by a Mechanism Involving Two One-Electron Steps

Abstract

We have employed rapid scan stopped-flow spectroscopy to examine whether the mechanism of oxidative dehalogenation catalyzed by C. fumago chloroperoxidase (CCPO) involves two consecutive one-electron steps or a single two-electron oxidation. First, we optimized the formation of CCPO compound I (CCPO-I) [Fe(IV)=O/porphyrin radical] and CCPO compound II (CCPO-II) [Fe(IV)=O] for use in double mixing rapid scan stopped-flow experiments. Reaction of CCPO-I with 2,4,6-trichlorophenol (TCP) quickly yielded CCPO-II. Reaction of CCPO-II, a one-electron oxidant, with TCP rapidly regenerated the ferric resting state of the enzyme. The rates of the reaction of both CCPO-I and -II with TCP are first-order with respect to [TCP]. In the absence of organic substrate, CCPO-I is slowly reduced to CCPO-II and then the ferric state. The ability of both CCPO-I and -II to carry out the oxidative dehalogenation reaction is consistent with a mechanism involving two consecutive one-electron oxidations. In contrast, reaction of CCPO-I with thioanisole generated the ferric enzyme with no evidence of CCPO-II, consistent with a single two-electron oxidation by insertion of an oxygen atom. The relative stability of CCPO-I and -II has allowed us to differentiate between one- and two-electron substrate oxidations using rapid scan stopped-flow techniques.

Single turnover studies of oxidative halophenol dehalogenation by horseradish peroxidase reveal a mechanism involving two consecutive one electron steps: Toward a functional halophenol bioremediation catalyst

“…Detailed studies have been performed regarding the oxidation of chlorophenols by lactoperoxidase [16], lignin peroxidase (LiP) [17], horseradish peroxidase (HRP) [18][19][20], dehaloperoxidase [21][22][23][24][25][26][27][28][29][30][31][32] and Caldariomyces fumago chloroperoxidase [33,34]. Among these peroxidases, HRP is an especially promising candidate for use as a bioremediation catalyst because of its (a) stability resulting in easier storage and handling, (b) ability to oxidize a large number of chlorophenols, (c) flexibility to function at wide ranges of temperature and pH, (d) and, most importantly, ready availability and relatively low cost [13,14,[35][36][37][38][39][40][41].…”

Chloroperoxidase Modified Electrode for Amperometric Determination of 2,4,6‐Trichlorophenol

“…The mechanism of the CPO-catalyzed oxidative dehalogenation of TCP has been elucidated [19]. CPO, like all peroxidases, follows a reaction cycle that uses H 2 O 2 to oxidize CPO into a reaction intermediate, which can undergo two one-electron reductions to regenerate the ferric state of the hemin moiety of the enzyme with concomitant TCP oxidation.…”

Research Progress on Dehalogenation Reaction

“…各种脱卤反应在环境保护 [1,2] 、生物化学 [3,4] 和有机 合成 [5,6] 等方面有重要应用, 特别是通过选择性脱卤反 应来实现 C-H 键的形成在有机合成中越来越受到化学 家们的重视. 在倡导绿色化学的今天, 许多温和而实用 性强的脱卤反应也不断涌现.…”