The Mechanism of Ageing of Phosphonylated Acetylcholinesterase

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Abstract
The extent of potential reaction of organophosphate-inhibited acetylcholinesterase [from the electric organ of Torpediniform narcine] decreases with time, a phenomenon called aging. Aging is due to dealkylation of the alkoxyl group of the residue bound to the enzyme. The rate of aging is proportional to the electron-donating capacity of the alkyl group. The aging of phosphophonylated cholinesterase also can be demonstrated using a phrenic nerve-diaphragm preparation. The same relationship between the rate of aging and the structure of the alkyl group was observed. Aging occurs much faster in electrically stimulated preparations than in resting preparations. This may be due to production of a more acidic environment for the enzyme at the active center by the products of hydrolysis of the acetylcholine released by stimulation.