Su Yunyou, Chen Lifeng, Bandy Brian, Yang Jian
College of Pharmacy and Nutrition, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, Canada S7N 5C9, Canada.
Open Microbiol J. 2008;2:100-6. doi: 10.2174/1874285800802010100. Epub 2008 Aug 12.
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.
五氯苯酚4-单加氧酶（PcpB）在嗜氯鞘氨醇菌的五氯苯酚生物降解途径中催化五氯苯酚的羟基化反应。来自两个不同研究小组的先前研究提出了相反的观点，即PcpB的催化产物是四氯对苯二酚（TCHQ）和四氯苯醌（TCBQ）。我们重新研究了PcpB催化产物的身份，因为TCHQ和TCBQ在水溶液中处于氧化还原平衡状态，并且先前研究中用于产物检测的化学试剂烟酰胺腺嘌呤二核苷酸磷酸（NADPH）、乙酸乙酯和谷胱甘肽可能会改变这种氧化还原平衡。在本研究中，我们研究了NADPH、乙酸乙酯和谷胱甘肽对氧化还原平衡和产物分布的影响。在新设计的实验条件下，我们明确证实PcpB的催化产物是TCHQ而不是TCBQ。我们还提出，TCBQ可能是由细菌细胞内的过氧化物酶非特异性产生的，并且TCBQ还原酶（PcpD）可能起到自我保护作用，而不是一种五氯苯酚降解酶。
