COPPER, ENZYMES, AND FERTILIZATION. 97 



biological element. It is widely diffused in the environment and 

 has been so since earliest geological time. Though listed among 

 the less active metals, it is capable of entering into a large variety 

 of combinations, including numerous organic unions. It is diffi- 

 cult to see how a living thing could avoid copper except by some 

 definite mechanism of exclusion. 



The absence of this is significant, but does not establish physio- 

 logical importance. Very possibly living things are mere sieves 

 that hold the copper back; very possibly, too, its marked concen- 

 tration in such tissues as the liver is a liability, by accident de- 

 pendent on other attributes and under ordinary circumstances negli- 

 gible. Still one would like to be certain, and in our present state 

 of knowledge this is impossible. Yet a negative answer, excluding 

 copper from the realm of physiological processes, even now ap- 

 pears unlikely. It is impossible to conceive the synthesis of respi- 

 ratory pigments, turacin, or any other product without thinking of 

 a long linkage of reactions inevitably affected, directly or other- 

 wise, by their final end result. 



2. Copper and Enzymes. 



Von Euler and Svanberg (loc. cit.) have shown that the addition 

 of saccharase results in a marked reduction of the free silver ions 

 in dilute solutions of silver nitrate. Since the silver did not be- 

 come colloidal under the influence of reductions, possibly due to 

 certain constituents of the enzyme preparation, these writers sug- 

 gest a binding of the silver ions to certain constituents of the 

 saccharase solution. 



Since such unions render the enzyme inactive, why not assume 

 that the constituent of the solution with which the metallic ions 

 combine is the enzyme itself, an organic co-enzyme, or both? 

 Such an assumption seems all the more reasonable because pro- 

 longed dialysis, I find, does not remove all the copper. Thus if 

 copper incapacitates at all, catalysis would be excluded in any case. 4 



4 It is not possible that certain differences of proportionality between the 

 effects of silver and mercury salts could be explained on this basis? Perhaps 

 too the recovery known as " The Danysz Phenomenon " results from a re- 

 distribution of metallic ions between enzyme and co-enzyme. Even if co- 

 enzyme and enzyme together make up, and are identical with, the entity, 

 enzyme, the allocation of Cu to different positions in this system might have 

 results essentially those suggested both in sense and in degree. 



