Organophosphorus Toxins

Decker, S.R Klabunde, J.S. Khaleel, A. Klabunde, K.J. Catalyzed destructive adsorption of environmental toxins with nanocrystalline metal oxides. Fluoro-, chloro-, bromocarbons, sulfur, and organophosphorus compounds. Environ. Sci. Technol. 2002, 36, 762-768. 

Dichlorvos (9.50) is an insecticide of reportedly wide use, the metabolites of which in humans include dichloroethanol and dimethyl phosphate. Like paraoxon, dichlorvos is hydrolyzed by human serum. However, the enzyme activities hydrolyzing the two substrates were shown to differ by a number of criteria [114], Clearly large gaps remain in our understanding of the human metabolism of organophosphorus insecticides and other toxins. A bacterial phosphodiesterase appears as a promising tool to understand the catalytic mechanisms of organophosphoric acid triester detoxification [115-117],... 

HYDROXYLAMINES, HYDROXAMATES AND OXIMATES AS ANTIDOTES FOR INTOXICATION BY ORGANOPHOSPHORUS TOXINS (CHEMICAL WARFARE AGENTS) AND... 

Nerve gases Probably the most widely stocked chemical agents liquid, gas or aerosol toxins belonging to the group of organophosphorus compounds, which are absorbed by the skin or lungs, usually within 20 to 30 minutes. 

With irreversible interactions, however, a single interaction will theoretically be sufficient. Furthermore, continuous or repeated exposure allows a cumulative effect dependent on the turnover of the toxin-receptor complex. An example of this is afforded by the organophosphorus compounds, which inhibit cholinesterase enzymes (see Aldridge (7) and chap. 7). 

The mechanism resembles that proposed for a phosphotriesterase (Fig. 12-24). The triesterase catalyzes detoxification of organophosphorus toxins such as parathion (Box 12-E) and seems to have evolved rapidly from a homologous protein of unknown function.721 The phosphotriesterase contains two Zn2+ ions in a dimetal center. An unusual structural feature is a carbamate group, formed from Lys 169 and C02, which provides a bridging ligand for the metal pair.721-725 A carbamylated lysine also functions in ribulose bisphos-phate carboxylase (Fig. 13-11). 

Toxins Alcohol (ethanol) consumption, scorpion venom, organophosphorus insecticides... 

With irreversible interactions, however, a single interaction will theoretically be sufficient. Furthermore, continuous or repeated exposure allows a cumulative effect dependent on the turnover of the toxin-receptor complex. An example of this is afforded by the organophosphorus compounds which inhibit cholinesterase enzymes (see Aldridge, 1996, and Chapter 7). This inhibition involves reaction with the active site of the enzyme which is often irreversible. Resynthesis of the enzyme is therefore a major factor governing the toxicity. Toxicity only occurs after a certain level of inhibition is achieved (around 50%). The irreversibility of the inhibition allows cumulative toxicity to occur after repeated exposures over an appropriate period of time relative to the enzyme resynthesis rate. 

Biosensors based on neuroreceptors can measure toxins or other chemical agents used in warfare. The use of acetylcholine receptors enables the determination of acetylcholine by the detection of a specific impedance compared with other neurotransmitters [93]. This receptor is associated with immobilized acetylcholinesterase, and is sensitive to its inhibitors, organophosphorus compounds and carbamates. The receptor is physically adsorbed onto a suitable sensor by immersing the sensitive tip of the sensor in a liposome solution containing the receptor. 

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