87 
small amount of the residue passed into solution. This mixture was 
then filtered and the filtrate tested toward tyrosin with and without 
hydrogen peroxide. While the solution containing hydrogen perox- 
ide showed the characteristic blackening with tyrosin after twelve 
hours and required 17.6 c. c. of 0.002 N permanganate to decolorize 
it,® the test without hydrogen peroxide remained colorless for two 
whole days. Bach concludes, therefore, that at ordinary dilutions 
hydrogen peroxide exerts no influence on fresh, normal tyrosinase. 
As the result of certain changes in the tyrosinase, however, which may 
be brought about naturally or by artificial means, whereby the fer- 
ment becomes greatly weakened, its activity toward tyrosin may 
be greatly increased by dilute hydrogen peroxide. He is therefore 
of the opinion that the simplest view to take of the weakening of 
tyrosinase and its partial restoration by hydrogen peroxide is to 
refer it to the destruction of its unstable oxygenase. 
In a more recent communication Bach ( 25 ) shows that it is impos- 
sible to oxidize tyrosin by the oxidase of Lactarius vellereus , and also 
that it is impossible to oxidize it by this peroxidase in the presence 
of hydrogen peroxide and a preparation of tyrosinase which had 
previously been destroyed by boiling. 
It has also been shown by Chodat ( 116a ) and also by Bach ( 21 » 22 ) that 
ordinary peroxidase and hydrogen peroxide are without action on 
tyrosin. It would seem, therefore, that tyrosinase presents us with 
a case of specific ferment action connected in some way with the 
chemical constitution of the substance oxidized, and that while the 
two oxidases, laccase and tyrosinase, are similarly constituted in the 
sense that each contains a peroxidase and an oxygenase, and that in 
each case the oxygenase component may be replaced by hydrogen 
peroxide, the two enzymes differ in the specific character of their 
peroxidase constituent. The peroxidase of laccase is specific in the 
sense that while it can activate hydrogen peroxide toward guaiacum, 
hydroquinone, pyrogallol, plienolphthalin, etc., it can not activate it 
toward tyrosin, and while the peroxidase of tyrosinase can activate 
hydrogen peroxide toward tyrosin, and certain other amino com- 
pounds, it can not activate it toward the laccase reagents. 
ANTI-TYROSINASE. 
According to Gessard ( 182 ), the blood serum of a rabbit which has 
been inoculated with vegetable tyrosinase at successive intervals, 
retards the action of the ferment on tyrosin to a considerable extent, 
so that a long interval is required for the solution of the ferment and 
a The excess of hydrogen peroxide remaining at the end of these experiments was 
in all cases removed by the addition of 1 c. c. of catalase solution. This quantity of 
catalase solution was sufficient to decompose 10 c. c. of a 1 per cent solution of hydro- 
gen peroxide in one minute. 
