Characterization of the Key Enzymes in Polycholorophenol Biodegradation

Washington State University, Pullman WA

Investigators

Abstract

Polychlorophenols are among the most pervasive organic pollutants in the United States. Several types of polychlorophenols are primarily introduced into the environment through their use as preservatives in the wood industry, as herbicides in agriculture, and as general biocides in consumer products. They persist in the environment because halogen substitution makes them recalcitrant to microbial degradation. Significantly we have identified and characterized several microbial enzymes involved in the degradation of those toxic compounds. The PIs characterization of these enzymes has revealed several novel reactions that prompt further investigation from both biochemical and structural perspectives. The PIs long-term goal is to develop a fundamental understanding of the degradation mechanisms and to define the parameters for the substrate specificity of all the participating enzymes in the biodegradation pathway of those xenobiotic pollutants. The target of the current research is focused on the comparative investigation of three monooxygenases (TcpA, TftD and PcpB) and one special dioxygenase (PcpA), all of which catalyze the dechlorination step in polychlorophenol biodegradations. In the breakdown process of those polychlorinated aromatic compounds, dechlorination is critical because partial or complete dechlorination must occur before ring-cleavage and the subsequent mineralization. However, enzymatic dechlorination has not been significantly investigated. This investigation is providing a comprehensive understanding of the unusual specificities and reactions catalyzed by those enzymes. It is contributing to the determination of the feasibility of modification of the structures of the active sites to broaden the substrate range or accelerate the kinetics. This may lead to better clean-up strategies for remediating toxic environmental sites. Broader impacts This research is improving the catalytic efficiency and range of substrate specificity for the biodegradative enzymes capable of bioremediation of xenobiotic pollutants. It is applying a multidisciplinary approach to the problem by combining biochemical, genetic, biophysical and mechanistic expertise. Two graduate students, including Emiliamo Sanchez, and several undergraduate students are participating in the research. High school students are also involved in the research through existing NSF-funded K-12 outreach programs at Washington State University, bringing enzymology, structural biology and environmental microbiology to the high school classroom and local Discovery Center.