82 
upon substances other than tyrosin. During the last few years this 
conduct of tyrosinase toward a large number of aromatic amino com- 
pounds has been studied, including the optical isomers of tyrosin, and 
also the effect of various amino compounds and other substances on 
the action of tyrosinase on tyrosin. Thus it has been found by Ber- 
trand and Rosenblatt ( 6fi ) to act equally well upon racemic and laevo- 
tyrosin. They found the tyrosinase from Russula queletti Fr., to 
give equal amounts of melanine with (d + 1) and 1-tyrosin, in a given 
time, without any separation of the racemic compound into its 
optically active components. According to Chodat and Staub ( 117 ) 
albumoses do not give a red color with tyrosinase. Such a coloration 
is produced by the action of tyrosinase on glycyl-tyrosin anhydride, 
indicating that possibly other peptids may give the reaction. In a 
continuation of their researches on the action of tyrosinase on the 
products of protein degradation, these authors ( 118 ) have observed 
that the oxidation of tyrosin by tyrosinase is diminished by certain 
amino acids, such as glycin, leucin, and alanin. They have found 
tyrosinase to act upon certain dipeptids, such as tyrosin anhydride, 
and glycyl-tyrosin anhydride, giving rise to yellow substances which 
do not become black, as does tyrosin itself. When, however, an amino 
acid, such as glycin, leucin, or alanin, is present, a red coloration 
similar to that resulting from tyrosin is obtained. Thus, a mixture of 
glycyl-tyrosin anhydride with glycin gives with tyrosinase a rose 
color, changing to bluish green ; with alanin it gives a deeper red, and 
with leucin a deep brown color. Phenyl-alanin is not acted on by 
tyrosinase. These observers conclude, therefore, that the action of the 
ferment does not depend altogether upon the presence of a benzene 
nucleus in an amino acid. They have also found that tyrosinase acts 
readily on p-cresol, less readily on m-cresol, and still less readily on 
o-cresol. As a rule they have observed tyrosinase to act most readily 
on the homologues of phenol, in which the side chains occupy the 
para- position, and in this respect the ferment seems to differ essen- 
tially from Millon’s reagent, which is apparently specific for benzene 
compounds containing one hydroxyl group, especially meta deriva- ij 
tives. According to Chodat and Staub (supra) the action of tyrosi- 
nase on p-cresol serves to distinguish the ferment from laccase. The 
addition of glycin or another amino acid greatly increases the rapidity 
of its action on p-cresol, giving rise to violet color which ultimately 
becomes blue with a reddish fluorescence. These authors conclude 
that tyrosinase may be employed as a reagent for tyrosin and that 
with the addition of amino acids, the ferment may also be employed 
to detect peptids containing tyrosin residues in the products of the 
digestion of protein. 
Bertrand ( 62 ) in his recent researches on melanogenesis, has also 
studied the action of tyrosinase from wheat bran on various com-' 
II 
