DAVID NACHMANSOHN 



In the great variety of nerve tissue which has been used as basis 

 for establishing the new concept, the enzyme was found to be an esterase 

 specific for acetylcholine, viz-, mammalian brain, lobster nerve, squid 

 fiber containing the giant axon, and the electric tissue. All show a 

 similar pattern, typical for choline esterase. In contrast, the hy- 

 drolysis patterns of the esterase of other organs — liver, kidney and 

 pancreas — differ greatly from that of choline esterase. The esterase 

 in these tissues shows several variations; but this could be expected, 

 since the physiological substrate is unknown and probably varies in 

 the different organs. Only in muscle (free of nerve endings) was an 

 enzyme obtained whose properties corresponded with those of choline 

 esterase. It is possible that propagation of an impulse in the muscle 

 fiber has the same mechanism as in the nerve fiber. But the presence 

 of choline esterase alone is not sufficient to permit any conclusion. 



Of special interest is the pattern obtained with purified choline 

 esterase. The enzyme extracted from the electric organ of E. electricus 

 has been purified to such a degree that one milligram of protein splits 

 three thousand milligrams of acetylcholine per hour. The rates of 

 hydrolysis of different svibstrates are exactly the same as those ob- 

 tained with freshly homogenized electric tissue. Thus, the enzyme 

 tested in fresh electric tissue is the same as that which is highly purified 

 and the parallelism established between voltage and enzyme activity 

 becomes particularly significant. 



Energy Source 



The electric organ also offers suitable material for investigating 

 the chemical reactions supplying the energy for the nerve action po- 

 tential. Both the electrical and the chemical energy released are in 

 the range of possible measurement, whereas, in ordinary nerves, the 

 methods available are not adequate for quantitative analysis. The 

 organ of Electrophorus electricus, for reasons discussed elsewhere, is again 

 particularly favorable for such a study. 



Measurements carried out on these fish have revealed some facts 

 about the chemical source of energy for the action potential. The 

 electric energy released externally per gram and impulse was found to 

 be 8 X 10~® gcal. This is the maximum external energy which may 

 be obtained under the condition that the external resistance is approxi- 



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