SIX FIGURES
Esterases, in the stricter sense of the word, are enzymes hydrolyzing carboxylic acid esters of mono-and polyhydric alcohols and phenols. There is a large body of biochemical data available to show that esterases differ froiii each other in respect to substrate preference and to their behavior towards various activators and inhibitors. The literature of the subject is so vast that it cannot be quoted in detail. Suffice to say that according to the generally accepted classification, esterases can be divided into two large classes, the aliesterases and the cliolinesterases (Richter and Croft, '42). 4liesterases hydrolyze carbosylic esters of N-free alcohols. They are subdivided into tv70 groups : lipases, the substrates of wliich a r e glycerides of long-chained fatty acids, aiid esterases, the substrates of which are short-cliained fatty acid esters of iiionoliydric alcohols and plienols. Cliolinesterases, on their part, are also subdivided into two groups: "true" or s1)ecific clioliiiesterases which hydrolyze acetylcholine preferentially, aiid ''pseudo " o r nonspecific eholinesterases which attack choliiie esters other than acetylcholine (Nachmaiisohn and Rothenberg, '44). Each group of enzymes has its specific inhibitors and/or activators. The inhibition and activation effects are just as characteristic as the substrate preferences. This worh lies l~eeii supported hy graiits f i oin tlir Donglns Smith Fouiidatioii for Medical lkseaicli of The CiiiveisitF of C1iic;ig.o. :iiid from the Pathology Study Section of the T'iiited States P u b l i c Heeltli SwTice.