ARE PEROXIDASES FERMENTS? 549 



for example, it be assumed that the laccase is a manganese 

 compound which readily undergoes hydrolytic dissociation 

 following the formula, E Mn + H 2 = EH 2 + MnO, it may 

 be at once appreciated why even a small amount of acid 

 would arrest the action. In case of other peroxidases iron 

 may play the same role. On the other hand, it must be proved 

 that there really are peroxidases which are active in an acid 

 medium and which are found to be free of manganese and 

 of iron. 34 



Efforts have also been made to solve the question of 

 the enzymic nature of peroxidases by study of their fer- 

 ment kinetics. Bach and Chodat have noted in oxidation of 

 pyrogallol by vegetable peroxidases that the amount of pur- 

 purogallin formed when there was excess of peroxidases 

 was in direct proportion to the amount of hydrogen peroxide, 

 but that when there was an excess of hydrogen peroxide it 

 was in direct proportion to the amount of peroxidase, and 

 that both these materials were used up in the process of 

 oxidation. This may be interpreted on the supposition that 

 in the formation of an intermediary product these substances 

 react upon each other in constant proportions a point dis- 

 tinctly opposed to the idea of a true ferment reaction. Other 

 observations along similar lines have been made by the 

 authors named in connection with oxidation of hydriodic 

 acid, by Czyhlarz and the author in case of the leukomal- 

 achite base, by Herzog 35 in case of the leuko base of brilliant- 

 green and in case of vanillin. It would be premature, how- 

 ever, to attempt to make any simple relative deductions from 

 all these complicated matters. It is to be kept in mind, 

 too, that the subject is further complicated by the possibility 

 of activation of ' ' zymogens, ' ' 36 and that for the present there 

 is no such thing as "isolation" of peroxidases, although re- 

 cently at least we have learned that peroxidase preparations 



"Cf. Bach, Ber. d. deutschen chem. Ges., J t S, 364, 1910. 

 85 R. O. Herzog, in association with A. Polotzky and A. Meier (Karlsruhe), 

 Zeitschr. f. physiol. Chem., 73, 247, 258, 1911. 



86 A. Bach, Ber. d. deutsch. chem. Ges., 40, 231, 1907. 



