ENZYMES CONCERNED WITH DIGESTION OF LIPIDS 53 



tion and physical similarity, have quite distinct patterns of action. 

 Myers 228 recorded marked variations in the action of serum cholinesterase 

 in a number of different species. Thus, the ratio of activity of serum 

 cholinesterases toward 0.06 M acetylcholine: 0.006 M benzoylcholine di- 

 minished progressively in mouse, rat, horse, man, and dog from 8.2 to 1.6. 

 In a later study, Myers 305 reported that, in 8 of the 13 species of animals 

 (10 mammals, 3 birds) examined, the pseudocholinesterases of the sera were 

 butyrocholinesterases; in four cases, they were shown to be propriono- 

 eholinesterases. The enzyme from pig serum could not be classified on the 

 basis of substrate specificity alone. Since human serum is able to induce 

 a slight hydrolysis of aeetyl-/3-methylcholine, Vincent and Parant 300 con- 

 cluded that it contained a small amount of the e-variety of cholinesterase. 



e-Cholinesterase was found in the erythrocytes of all animals which have 

 been investigated. Mounter and Whittaker 210 reported that the cholin- 

 esterase of horse erythrocytes closely resembles that prepared from the 

 red blood cells of human blood in specificity and physical properties. 

 Vitamin E deficiency has been shown to reduce the erythrocyte cholin- 

 esterase of rats. 306 When phenothiazine was added to the diet, the pro- 

 portion of cholinesterase activity was shown to increase almost to the orig- 

 inal level. The erythrocytes of the tocopherol-deficient rats became sus- 

 ceptible to hemolysis by dialuric acid; this sensitivity was removed by 

 the addition of phenothiazine to the diet. 



b'. Cholinesterases in Brain and Nervous Tissue: Brain and nervous 

 tissue is an important site for cholinesterases. This is to be expected be- 

 cause of the prominent part which acetylcholine plays in the functioning 

 of this tissue. The e-type of cholinesterase has generally been accepted as 

 the main variety, if not the only type of cholinesterase, in the brain tissue 

 of all species of animals investigated to date. 185 - 186 - 189 ' 206,307-311 However, 

 Ord and Thompson 312 noted that cholinesterases, prepared from different 

 areas of human and other mammalian brains, were able in all cases to 

 effect a measurable degree of hydrolysis of benzoylcholine and of butyryl- 

 choline. These workers suggest that a "butyrocholinesterase" occurs in 

 human nervous tissue which closely resembles the pseudocholinesterase in 



306 D. K. Myers, Biochem. J., 55, 67-79 (1953). 



306 H. B. Collier and E. E. Dellert, XlXth Intern. Congress, Abst., Montreal, 1953, pp. 

 274-275. 



307 B. Mendel and H. Rudney, Science, 98, 201-202 (1943). 



308 D. Nachmansohn and M. A. Rothenberg, /. Biol. Chen., 158, 653-666 (1945). 



309 V. P. Whittaker, Biochem. J., U, xlvi-xlvii (1949). 



310 J. M. Little, Am. J. Physiol, 153, 436-443 (1948). 



311 J. M. Little, Am. J. Physiol, 155, 60-63 (1948). 



312 M. G. Ord and R. H. S. Thompson, Biochem. J., 51, 245-251 (1952). 



