544 OXIDATION FERMENTS 



60 C. than at 38 C. 16 The tyrosinases, a special variety of 

 peroxidases, dealt with at length in connection with the 

 formation of melanin (Vol. I of this series, pp. 527-536, 

 Chemistry of the Tissues), are thermolabile in a high degree. 



Another rather characteristic point of difference between 

 the oxygen convection by haemoglobin and by the peroxidases 

 was pointed out by the author's associate and himself. In 

 graphic registration of the results obtained by the spectro- 

 photometric malachite-green method, using the time values 

 as abscissas and the appropriate amounts of oxidation prod- 

 uct as ordinates, it became evident that the catalyzing re- 

 actions of haematin were represented by almost straight lines 

 which proceeded from the coordinate starting point at dif- 

 ferent angles. The reaction of true animal peroxidases 

 (obtained from pus cells), however, correspond to curves 

 which after a constant, more or less sharp rise suddenly 

 turn toward the horizontal and continue parallel to the 

 abscissa axis. This corresponds closely with the curves 

 which Bach and Chodat repeatedly observed in case of vege- 

 table peroxidases. Bach, 17 therefore (as well as Lesser 18 

 and Buckmaster), 19 is of the opinion that haematin behaves 

 somewhat like a chemically definite catalysator, while the 

 action of true animal peroxidases approaches that of other 

 ferments. 



We, therefore, have reason for the time being to regard 

 the blood coloring matter as a " pseud operoxidase" in con- 

 tradistinction to the true oxidases. 



On the other hand again, W. Madelung is of the opinion 

 that the activation of peroxides by the haemoglobin is func- 

 tionally not different from their activation by the tissue 

 peroxidases, inasmuch as apparently there also exist in the 



16 F. Battelli and L. Stern, 1. c., p. 88. 



17 A. Bach (Geneva), Biochem. Centralbl., 9, 1909 Sep., p. 20. 



18 E. J. Lesser, Zeitschr. f. Biol., 49, 571, 1907. 



19 A. Buckmaster, Jour, of Physiol., 35, Proc. XXXV, 1907; 37, Proc. XI, 

 1908. 



