[Organophosphorus compounds: classification and enzyme reactions].

Organophosphorus compounds are derivatives of phosphoric, phosphonic or phosphinic acids whose oxygen atoms bound directly to the phosphorus atom can be substituted by sulphur or nitrogen atoms. These compounds represent a large group of organic compounds used primarily as pesticides. Some are used as drugs and the most toxic compounds as nerve agents. Acute toxicity of organophosphorus compounds is due to the inhibition of acetylcholinesterase, the critical enzyme in neurotransmission. Organophosphorus compounds whose sulphur atom creates a coordinative covalent bond with the phosphor atom are not acetylcholinesterase inhibitors. To become biologically active these compounds must transform into their oxo analogues, passing through spontaneous or biotransformation reactions. Biotransformation reactions of organophosphorus compounds involve a large number of enzymatic reactions that can make them more or less toxic, or even non-toxic for acetylcholinesterase. The classification of organophosphorus compounds in this paper considers the nature of groups bound directly to the central phosphorus atom. The paper describes the enzymes taking part in biotransformation of organophosphorus compounds and gives examples of their reactions.