Organofluoride ammonium compounds: a new group of reversible inhibitors of cholinesterases of various animals.

Abstract

The efficiency of cholinergically active compounds depends on both their spatial structure and physicochemical properties. The extent of hydrophobicity of the cholinesterase effectors is crucial for their efficiency [1]. However, the introduction of nonpolar substituents is accompanied by a significant change in the size and conformation of the molecule, which hampers differential approach to structure effects. In this regard, fluorine-containing compounds are of special interest. For example, the introduction of three fluorine atoms into the methyl group only slightly increases its volume but almost twofold increases the hydrophobicity constant, π ( = 0.50 , = 0.88 [2]). In view of this, we performed a comparative analysis of the ability of a series of organofluoride ammonium compounds [3, 4] and their unsubstituted analogues to inhibit the activity of cholinesterases of various origins. Simultaneously, we analyzed the conformational characteristics and the geometry of these effectors. We used purified preparations of human erythrocyte acetylcholinesterase (EC 3.1.1.7) and horse blood serum cholinesterase (EC 3.1.1.8) with specific activities of 1.2 and 9.6 units, respectively (Perm Research Institute of Vaccines and Sera). We also studied cholinesterases from the brain of the frog Rana temporaria and the optical ganglion of the Pacific squid Todarodes pacificus . The supernatant solutions obtained after centrifugation of aqueous homogenates of frog brains and squid optical ganglia (45 and 3 mg/ml, respectively) at 800 g for 15 min served as the source of frog and squid cholinesterases [5]. Acetylthiocholine iodide (Chemapol) was used as a substrate. The catalytic activities of cholinesterases were determined at 25i C and pH 7.5 colorimetrically according to Ellman [6]. We analyzed the following compounds as inhibitors of cholinesterases: