Double effect of organic amines (activation and inhibition) on the phosphotriesterase

The kinetic behavior of the phosphotriesterase in the presence of organic a mines (diethylamine, diisopropylamine, triethylamine, pyridine and others) capable of activating the enzyme at the concentration up to 0.10 M and inhi biting it at higher concentrations is described. The form acting as activat or in a solution is the nonprotonated form of amines and the value of activ ation effect depends on pK(a) of amine and its structure. The activation by amines at the above concentrations has a noncompetitive character, whereas the inhibition at higher concentrations has competitive one. The mechanism of phosphotriesterase action in the presence of amines is discussed. (C) 2 000 Elsevier Science B.V. All rights reserved.