544 ANNALS NEW YORK ACADEMY OF SCIENCES 



merely a reflection of the state of the serum proteins. Faber^'' has 

 found that there is a direct proportionality between serum cholin- 

 esterase activities and the concentration of serum albumin, but not 

 between these activities and the concentration of total serum protein 

 or that of the serum globulin. This, of course, does not imply that 

 cholinesterase is an albumin. Faber"^ has noted that, in proteinurias, 

 the serum cholinesterase activities remain high, relative to the concen- 

 tration of the serum albumin. There is an indication, in these observa- 

 tions, that the formation of serum cholinesterase parallels that of serum 

 albumin. 



We have already discussed the effects of DFP on the in vivo activity 

 of serum, red cell, and brain cholinesterases. There are, in the litera- 

 ture, similar studies on other drugs. Perhaps one of the most detailed 

 is that of Schutz,^^' *'^' '° concerning the effect of barbiturates. This 

 investigator noted that the prolonged administration of these drugs, in 

 man and animals, resulted in marked decreases of serum cholinesterase 

 activity, although these drugs in concentrations of about 0.01 M do 

 not inhibit the in vitro serum cholinesterase activity. He also ob- 

 served that such prolonged administration in animals resulted in in vivo 

 decreases of brain, spinal cord, and muscle cholinesterase activity. His 

 explanation was that the barbiturates decreased the activity of the 

 cholinergic system and, hence, the demand for cholinesterase. Such 

 an explanation is, of course, teleological and demands direct proof of 

 decreased synthesis of the cholinesterases involved. 



CONCLUSION 



As a conclusion to this review, it may be of value to emphasize certain 

 general points. The literature, as well as our own data, indicates that 

 we cannot speak of "one" cholinesterase, identical in its properties, no 

 matter where it may be found. Within one species, the enzyme differs, 

 in certain respects, from tissue to tissue, and the enzyme of a given tis- 

 sue may differ from species to species. Perhaps, then, it would be more 

 proper to speak of a "family" of cholinesterases, the members of which 

 resemble each other in some attributes and differ in others. Classifi- 

 cation into certain groups may now be possible, but even within such 

 groups, differences in properties may occur. Considerably more ex- 

 perimental work with various criteria of enzyme action is necessary, in 

 order to achieve a more satisfactory classification. The writer believes 

 that many of the controversies on the properties of cholinesterase which 

 have occurred in the literature will be resolved, if the foregoing consid- 

 erations are kept in mind. 



