Description:
Malathion is an organophosphate pesticide commonly used in the United States for controlling mosquito populations. The toxicity of malathion is low but acute exposure in high doses may cause a variety of symptoms including nausea, dizziness, or confusion. Malaoxon is a potent cholinesterase inhibitor that can be formed from malathion under certain conditions. Exposure to malaoxon can lead to complications in the central nervous system (Edwards, 2006. US Environmental Protection Agency - Prevention, Pesticides and Toxic Substances EPA 738-R-06-030). The predominant biodegradation pathway for malathion involves formation of mono- and diacid metabolites through carboxylesterase activity. Oxidative desulfurization and demethylation leads to complete mineralization. Other minor routes of metabolism include initial oxidation to remove sulfur and methyl groups ([http://www.ncbi.nlm.nih.gov/pubmed/402103|Laveglia and Dahm, 1977]). Pseudomonas aeruginosa AA112 is able to use malathion as a sole carbon source. [http://www.ncbi.nlm.nih.gov/pubmed/17896475|Abo-Amer (2007)] observed the formation of diethylsuccinate and succinate metabolites. The intermediate steps in this pathway have not been characterized. However, the reduction of -SH to -H (diethyl 2-mercaptosuccinate -> diethylsuccinate) may be abiotic ([http://www.ncbi.nlm.nih.gov/pubmed/12713326|Hebting et al., 2003]).