ORGANOPHOSPHATES

The organophosphate compounds also react at the esteratic site of AChE.In general, however, they are much less selective than are the carbamates, inhibiting many enzymes that contain a serine molecule at an active center. The organophosphate compounds have this general structure:
Parathion and malathion (insecticides) are thiophosphates that must be converted to oxyanalogues to become active. The organophosphates, except for echothiophate, are very lipid soluble.In the interaction of isoflurophate with AChE, a phosphorylated intermediate is formed and fluoride is released.An important characteristic of the organophosphate- induced inhibition is that the bond between the phosphate and the enzyme is very stable.While the regeneration of most carbamylated enzymes occurs with a half-life of minutes or hours, the recovery of a phosphorylated enzyme is generally measured in days. These agents are referred to, therefore, as irreversible inhibitors.