81 
of animal tyrosinase, while the effect of the addition of small amounts 
of alkali is to cause a distinct increase in the activity of the ferment. 
Of the metallic catalyzers tested, viz, 1 per cent solutions of the sul- 
phates of manganese, iron (ferrous), copper, and nickel, only man- 
ganese was found to increase the rate of production of the melanine 
by animal tyrosinase. With the animal tyrosinase much greater in- 
creases in the quantities of melanine produced resulted from increases 
in the quantities of ferment ; in other words, while the further addi- 
tion of animal tyrosinase over and above a certain amount caused 
no corresponding increase in the quantity of melanine produced, no 
distinct hindrance of the process, such as that brought about by 
large amounts of vegetable tyrosinase, was observed. 
As already indicated in the above, Bach’s ( 23 ) permanganate 
method for the determination of melanine has yielded more con- 
cordant results in the study of the kinetics of melanine formation by 
tyrosinase than any that have been employed up to the present time. 
Without going into details, this author ( 24 ) has shown that in the pro- 
duction of melanine from tyrosin, tyrosinase undoubtedly obeys the 
law of mass action, the departures therefrom observed during the 
later phases of the reaction being due to the fact that the activity of 
the ferment becomes more or less exhausted during the course of the 
reaction, this exhaustion being the more rapid the greater the concen- 
tration of the ferment or substrat; that is, the greater the velocity 
of the reaction. 
THE ACTION OF TYROSINASE OX VARIOUS AMINO COMPOUNDS, ESPE- 
CIALLY THE PRODUCTS OF PROTEIN DEGRADATION. 
It has been pointed out that laccase is not specific as an oxygen car- 
rier, but that it can effect the oxidation of various easily oxidizable 
substances such as guaiacum, guaiacol, hydroquinone, phenolphthalin, 
etc. The question naturally suggests itself in this connection, Is the 
action of tvrosinase confined to tvrosin or can it likewise accom- 
plish the oxidation of other aromatic amino compounds? The 
earlier workers in this field were doubtless inclined to look upon it as 
specific in its action on tyrosin. Thus vegetable tyrosinase (from 
Russula delica) was employed by Bougault ( 72 ) as a reagent for the 
detection of tyrosin in various animal products, and by Harlay ( 206 ) 
for the detection of tyrosin in the products of the pancreatic 
digestion of fibrin, and also in the products of the proteolysis in 
germinating grain. With the products of the pancreatic digestion 
of fibrin, tyrosinase gives a reddish brown color (tyrosin) ; with the 
products resulting from the peptic digestion of fibrin, Harlay found 
the extract of russula to give a green color. This indicates, of course, 
the absence of tyrosin, but it also indicates that tyrosinase can act 
11670— Bull. 59—10 6 
