Enzymes 213 



is rather surprising because naphthol AS is a derivative of 

 y8-naphthol. Benzoates as substrates give pictures indistin- 

 guishable from those produced by the acetates. There is no 

 histochemical support for the existence of a special acetyl- 

 esterase.^^^ 



Most of the localizations of cholinesterases are entirely dif- 

 ferent from those of the aliesterases, although at some sites 

 the localizations coincide (livers of some species; pancreas 

 of the dog). In the sympathetic ganglia, esterase is found 

 usually (but not always) in the bodies of the ganglion cells 

 themselves, whereas cholinesterase is found in the aboriza- 

 tions around them. 10^ M eserine completely abolishes all 

 activity if lauroyl- or myristoylcholine are used as substrates. 

 In the case of palmitoylcholine, inhibition is only partial. 

 This difference may be due to the fact that the inhibitoi un- 

 dergoes considerable decomposition on prolonged incuba- 

 tion. 



With regard to the long-chained fatty acid ester method 

 for cholinesterase, two important points must be mentioned: 



1. There are marked species and organ differences in re- 

 spect to preference for the various substrates. Although, as 

 a rule, lauroylcholine is hydrolyzed much faster than palmi- 

 toylcholine, rat and pigeon tissues and human adrenal me- 

 dulla split palmitoylcholine as fast as, or faster than, lauroyl- 

 choline. The spermatic elements of the mouse testis show 

 no reaction with lauroylcholine, a moderate reaction with 

 myristoylcholine, and an intense one with palmitoylcholine, 

 although other tissues of the mouse behave in the opposite 

 way. The pattern of fine localization is also different with 

 the three substrates. With lauroylchoHne it is the nuclei 

 which show the highest activity; with palmitoylcholine, cy- 

 toplasmic structures. These findings would indicate that the 

 cholinesterases demonstrable by this method form a family 



126. Jansen, E. F., Jang, R., and MacDonnell, L. R.: Arch. Biochem., 

 15:415, 1947; Jansen, E. F., Nutting, M. D. F., and Balls, A. K.: J. Biol. 

 Chem., 175:975, 1948. 



