The Catalytic Product of Pentachlorophenol 4-Monooxygenase is Tetra-chlorohydroquinone rather than Tetrachlorobenzoquinone
Yunyou Su, Lifeng Chen, Brian Bandy, Jian Yang*
Identifiers and Pagination:Year: 2008
First Page: 100
Last Page: 106
Publisher Id: TOMICROJ-2-100
Article History:Received Date: 30/6/2008
Revision Received Date: 23/7/2006
Acceptance Date: 23/7/2008
Electronic publication date: 12/8/2008
Collection year: 2008
open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.
Pentachlorophenol 4-monooxygenase (PcpB) catalyzes the hydroxylation of pentachlorophenol in the pentachlorophenol biodegradation pathway in Sphingobium chlorophenolicum. Previous studies from two different research groups proposed oppositely that the catalytic product of PcpB was tetrachlorohydroquinone (TCHQ) and tetrachlorobenzoquinone (TCBQ). We re-examined the identity of the catalytic product of PcpB, because TCHQ and TCBQ are present in a redox-equilibrium in aqueous solutions and the chemical reagents NADPH, ethyl acetate and glutathione used for the product detection in the previous studies may shift the redox-equilibrium. In this study, we investigated the effects of NADPH, ethyl acetate and glutathione on the redox-equilibrium and product distribution. Under newly designed experimental conditions, we confirmed unambiguously that the catalytic product of PcpB is TCHQ instead of TCBQ. We also propose that TCBQ may be produced non-specifically by peroxidases within the bacterial cells and that TCBQ reductase (PcpD) might act as a self-protective rather than a PCP-degradation enzyme.