Microsomal oxidations desulfuration

Microsomal oxidations may be subdivided into aromatic hydroxylation aliphatic hydroxylation alicyclic hydroxylation heterocyclic hydroxylation N-, S-, and O-dealkylation N-oxidation N-hydroxylation S-oxidation desulfuration deamination and dehalogenation. 

De Matteis, F., Covalent binding of sulphur to microsomes and loss of cytochrome P450 during oxidative desulfuration of several chemicals, Molec. Pharmacol, 10,849-854,1974. 

Some of these irreversible AChEI insecticides have a sulfur atom bonded to the phosphorus atom ith a coordinate-covalent bond. These compounds exhibit little AChEI activity, but they are rapidly bioactivated via desulfurization by microsomal oxidation in insects to afford the corresponding oxo derivatives (phosphate esters), hich are quite potent. A good example of this bioactivation phenomenon is illustrated by the commercially available insecticide parathion and its bioactivation to a toxic metabolite paraoxon. 

F. de Matteis, Covalent binding of sulfur to microsomes and loss of cytochrome P-450 during the oxidative desulfuration of several compounds, Mol. Pharmacol. 10, 849-854 (1974). 

As mentioned in Chapter 8, microsomal desulfuration and sulfoxidation of insecticides represent oxidative activation processes. It would seem that plant-stimulated enhancement of such metabolism would be advantageous, making some insecticides more toxic. This... 

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