PURIFICATION AND PROPERTIES OF THE INDUCIBLE CHOLINESTERASE OF PSEUDOMONAS FLUORESCENS (GOLDSTEIN)

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Abstract
The inducible cholinesterase produced by the Goldstein strain of P. fluorescens was purified to a state of electrophoretic homogeneity. The enzyme, which resembles an acetylcholinesterase in its substrate specificity, has a high affinity for pcetylcholine and propionylcholine. The estimated values of Km at pH 7.4 and 37[degree]C are 1.4 x 10-5 [image] for acetylcholine and 2.0 x 10-5 [image] for propionylcholine. The bacterial cholinesterase reacts slowly with tetraethyl pyrophosphate (TEPP) and diisopropyl phosphorofluoridate (DFP) but comparatively rapidly with ethyl N,N-dimethylphosphoramidocyanidate (Tabun). Bimolecular rate constants range from 7.7 mol-1 min-1 for TEPP to 7.4 x 104 mol-1 min-1 for Tabun. The reactions of the cholinesterase depend upon the ionic state of groups in the enzyme whose pKa values are in the same range as those reported for other esterases. The enzyme may be similar in structure to other cholinesterases, and both histidine and serine may be involved in its activities.