ENZYMES CONCERNED WITH DIGESTION OF LIPIDS 29 



esters. Augustinsson and Naehmansohn 184 proposed that the term "acetyl- 

 cholinesterase" he used to designate the specific acetylcholine-splitting 

 enzyme. Zeller and Bissegger 186 have referred to the "tnio" type as the 

 "r-type," because it is present in erythrocytes. 



2. "Pseudo" m or "non-specific' choline st erase, which hydrolyzes not only 

 acetylcholine but compounds closely related to acetylcholine, as well as 

 simple esters such as methyl butyrate, is the designation of a second eholin- 

 esterase. Alles and Hawes 187 consider this terminology inadvisable. This 

 type of cholinesterase is referred to by Zeller and Bissegger 185 as "s-type," 

 because it is present in serum. Moreover, these workers consider that the 

 .s and e nomenclature is preferable to "serum" and "erythrocyte," since 

 these enzymes are found in tissues other than the aforementioned. On the 

 other hand, the letter designations s and e remind one of the original source 

 of the respective enzymes, i.e., human blood. 



3. "Ophiocholinesterase," "coluber cholinesterase" (coluber = snake) L. or 

 simply the "c" type. 164 This cholinesterase, obtained from cobra venom, 

 apparently differs from the e and s types. 



There is some question as to whether or not the number of types of cholin- 

 esterase should be limited to three. The variations in activity of the en- 

 zyme prepared from various tissues may be due to the protein moiety of 

 the enzyme in question. Zeller 164 indicates that these proteins may well be 

 specific not only with regard to species but also with relation to organs. 



As an example of such variations in connection with the s-enzyme, 

 Zeller 188 found that cholinesterases from human, horse, and guinea pig sera 

 presented different degrees of inhibition in response to such inhibitors as 

 sulfonamides, papaverine, and percaine. In another case, the action of the 

 enzyme prepared from the flatworm, Planaria dorotocephala, was inhibited 

 to a lesser degree by eserine and by other amines than was that from human 

 red cells; however, in other respects the Planaria enzyme acted as a "true" 

 cholinesterase. 189 Augustinsson 1HU showed that the cholinesterase of the 

 Roman land-snail (Helix pomatia) did not fit into either of the two afore- 

 mentioned categories. Further proof of the fact that at least two enzymes 

 exist which are capable of hydrolyzing choline esters is to be found in the 



184 K. B. Augustinsson and D. Naehmansohn, J. Biol. Chem., 179, 543-559 ( 1040). 



185 PI A. Zeller and A. Bissegger, Heir. Chim. Acta, 26, 1610-1630 ( 1043). 



186 B. Mendel and H. Rudnev, Biochem. J., 37, 50-63 (1043). 



187 G. A. Alles and R. C. Hawes, Science, 100, 75 (1044). 



188 E. A. Zeller, Helv. Physiol. Pharmacol. Acta, 2, C23-C24 (1044). 



189 R. D. Hawkins and B. Mendel. J. Cellular Comp. Physiol., 27, 60-85 (1046). 



190 K. B. Augustinsson, Biochem. J., /,0, 343-340 (1046). 



