THE HISTOCHEMICAL SPECIFICITY OF CHOLINESTERASES

On the basis of a review of the biochemical and histochemical literature, all esterases are divided into the eserine-resistant esterases (aliesterases) and the eserine-sensitive esterases (cholinesterases). It has previously been demonstrated by histochemical study that a wide spectrum of enzymes exists among the aliesterases; the present study is concentrated on the cholinesterases. The myoneural junction in four species; man, dog, rat, and mouse, was studied by histochemical techniques utilizing both choline esters and non-choline esters as substrates, and under the influence of various physical and chemical agents. On the basis of this study, it is demonstrated that none of the biochemical classifications or `types' of cholinesterases can be defended, and that the cholinesterases of the various species and tissues should therefore be viewed as a family of enzymes, forming a spectrum with multiple overlapping and differences with respect to physical properties, effects of inhibitors and substrate specificities.