84 
gen derivatives of the polypeptids were not acted upon. The action 
of tyrosinase on a polypeptid containing tyrosin was modified to 
some extent by various amino acids. Thus the action was greatly 
accelerated by 1-prolin, whereas it was retarded by aspartic and 
glutaminic acids. Prolin was found to act especially energetically 
in augmenting the action of tyrosinase on glycyi-l-tyrosin anhydride. 
They also found tyrosinase to act on phenol, giving a brown color, 
and here again the color produced by the action of tyrosinase was 
modified by amino acids. Thus gly cocoll and phenol gave a cochineal 
color, and prolin and phenol gave a violet reaction. These authors 
conclude that the character of the pigment resulting from the action 
of tyrosinase on tyrosin is dependent upon the combination in which 
the tyrosin exists. In the free state it is colored differently from 
what it is when in the anhydride or in the polypeptids. The amino 
acids when present apparently take part in the production of the 
pigment. In a later communication ( 2 ) these authors point out that 
tyrosinase acts rapidly on d-alanyl-l-tyrosin, and on 1-leucyl-l- 
tyrosin. They also found it to act on adrenalin with the rapid pro- 
duction of a red color and ultimately dark red flocculi. It was also 
found to act on the three optical isomers of adrenalin with equal 
rapidity. 
OX THE NATURE OF TYROSINASE. 
Bach and Chodat ( 2S ) (see p. 118-120) have shown that laccase is 
composed of two distinct substances, an oxygenase — that is, a sub- 
stance which forms a peroxide by taking up of oxygen and which 
is replaceable by hydrogen peroxide, — and a peroxidase, which 
activates this peroxide or the hydrogen peroxide added. According 
to this conception, the system, peroxidase + hydro-peroxide, is to all 
intents and purposes identical with the oxidases in its general behav- 
ior toward readily oxidizable substances. The question, therefore, 
naturally suggests itself in this connection. Is tyrosinase similarly 
constituted? In other words, Is this oxidase composed of a specific 
peroxidase and an oxygenase, and can other peroxides, such as 
hydrogen peroxide, take the part of the oxygenase in tyrosinase 
oxidations? Bach ( 21 ) has attempted to answer these questions. 
According to this observer, tyrosinase contains a peroxidase and an 
oxygenase, and it is to the former that it owes its specific power to 
oxidize tyrosin and similarly constituted substances, since hydrogen 
peroxide may be employed in the place of the oxygenase contained 
in tyrosinase in accomplishing the oxidation of tyrosin. Thus he ob- 
served that a fresh aqueous extract of young potato tubers rapidly 
oxidizes and blackens a solution of tyrosin, whereas if the expressed 
juice of finely ground new potatoes be allowed to stand for twenty- 
