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Parathion (O,O-diethy-O-p-nitrophenyl phosphorothioate) is an organophosphate compound and is one of the most toxic insecticides registered with the U.S. Environmental Protection Agency (EPA). On agricultural crops it was used widely as a broad spectrum insecticide, acaricide, fumigant and nematocide. In 1991 parathion became a Restricted Use Pesticide (RUP). Parathion is well tolerated by crops, does not easily leach through soil and may be degraded by soil microorganisms within weeks. Degradation of parathion by sunlight or liver enzymes results in the active compound paraoxon which interferes with the nervous system through cholinesterase inhibition. Extreme toxicity combined with the ease of exposure has resulted in numerous human and non-pest species deaths. The immediate aerobic metabolic breakdown product of parathion, PNP or p-nitrophenol, was listed as a priority pollutant in 1979 by the US EPA.
This pathway is based on Munnecke and Hsieh, 1976.
The following is a text-format parathion pathway map. Organisms which can initiate the pathway are given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions.
|Graphical Map (8k)| |--------------------Graphical Map (11k)--------------------|
Parathion Parathion Parathion
Mixed culture Flavobacterium sp. ATCC 27551 Mixed culture
Brevundimonas diminuta MG
| | |
| | | aryldialkyl-
| E | | phosphatase
| | |
| | |
v | v
Aminoparathion | Paraoxon
| | |
| | aryldialkyl- +-------| aryldialkyl-
| F | phosphatase | | phosphatase
|--------------------------+ |--------------------------+ |
| | | | | |
v v v | v v
Diethylthio- |
p-Aminophenol <---------+ phosphoric acid | p-Nitrophenol
| | | | |
| | | | |
| 4-amino- from the | B | |
| phenol csab pathway | | |
| dehydrogenase | +------------------+ |
v v v v
Diethyl- to the
p-Benzoquinone phosphoric acid 4-Nitrophenol
| pathway
|
|
|
|
v
to the
4-Nitrophenol
pathway
Page Author(s): Cathy Cornett
April 25, 2008 Contact Us
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