Abstract

COMPUTATIONAL ANALYSIS OF BIODEGRADATION PATHWAYS FOR CHLORPYRYFOS USING EAWAG-BIOCATALYSIS/ BIODEGRADATION DATABASE PATHWAY PREDICTION SYSTEM

Seema Khan*, Kakoli Dutt,Veena Garg

Abstract

Introduction: Computational tools like pathway prediction systems are in vogue to examine the extent of degradation and possible pathways for exploration of degradative abilities of diverse microorganisms. They also give an idea of the tentative end products of the biodegradation mechanism. In-silico approach is mainly used in designing the experiments for biodegradation leading to bioremediation. Chlorpyrifos is a toxic organophosphate insecticide whose degradation pathway has not been extensively studied. It forms more toxic 3, 5, 6-trichloropyridin-2-ol which causes cancer thus, making it necessary to study its possible biodegradation mechanism. Methodology: In this study, eMolecules database and EAWAGBiocatalysis/Biodegradation Database-Pathway Prediction System (EAWAG-BBD-PPS), formerly called University of Minnesota Biocatalysis/Biodegradation Database-Pathway Prediction System (UMBBD-PPS), have been used to predict the degradation pathways of O,O-Diethyl O-3,5,6-trichloro-2-pyridyl phosphothiorate (chlorpyrifos). Intermediate compounds have been named using ChemDraw Ultra 8.0.6. Result: The predicted pathway showed that aerobic transformation of chlorpyrifos leads to formation of more toxic compounds viz. 3,5,6-tri-chloro-pyridinol (TCP) and diethylthiophosphoric acid (DETP). Further, aerobic transformation was not easy. De-chlorination and ring cleavage of TCP, which occurred much later in the pathway formed 2-hydroxyacetate which was metabolized through KEGG. DETP eventually produced thiophosphate and ethylphosphate which are much simpler and non-toxic and can mineralize into ethanol. Conclusion: Hence, it is concluded that plausible pathways predicted by EAWAG BBD-PPS explain microbial degradation mechanism and can aid in designing pesticide biodegradation/bioremediation experiments. It can be used to efficiently design microbial consortium that can completely mineralize chlorpyrifos or any other xenobiotic, thereby eliminating it from the environment.

Keywords: Biodegradation, Bioremediation, Computational analysis, Chlorpyrifos, In-silico, O, O-Diethyl O-3, 5, 6-trichloro-2-pyridyl phosphothiorate.