_ 20,2 Brill and Brown: Philippine Papain 187 
hole in the desk, protected from the sunlight most of the time 
since. Apparently papain may lose its activity with age, and 
this probably accounts for much of the inferior papain found 
in the market. 
The papain used by us was furnished by the Bureau of 
Science, Manila, Philippine Islands. The only deviation from 
Pratt’s procedure introduced by us was the use of a 10 per cent 
solution of skimmed-milk powder as the substrate instead of 
the sweetened, condensed, skimmed milk. The milk powder is 
more readily handled and remains sweet for an indefinite period 
when open to the air. It was, therefore, substituted for the 
Sweetened, condensed, skimmed milk which had been used by 
Pratt. Curve 1 is for sundried papain; curve 2, for alcohol- 
precipitated papain; curve 3, for alcohol-precipitated papain 
with milk that had been dialyzed at 20° C. for fourteen hours; 
curve 4, for alcohol-precipitated papain that had been dialyzed 
at 20° C. for fourteen hours; curve 5, for papain solution that 
stood at a temperature of 0° to 5° C. for seventeen hours. 
Our results are in accord with those of Pratt, who found the 
alcohol-precipitated enzyme to be more active than the sundried 
material. Curve 4 was determined in the hope that a separation 
of the papain from any co-enzyme might be made by dialysis 
and the co-enzyme identified, and curve 8, that the mineral salts 
present in milk might be removed. Curve 3 shows greater 
activity than does any other curve in fig. 1. Curve 4 shows much 
less activity than curve 1. To determine whether the lessened 
activity was due to the removal of a co-enzyme or to a partial 
autolysis of the enzyme, the experiment shown by curve 5 and 
‘ another (the curve for which is not included) were carried out. 
Curve 5 shows lessened activity of the enzyme, which indicates 
that the enzyme decomposes at a temperature as low as 0° to 
5° C. in the presence of water. The unrecorded curve showed 
a maximum digestion of 10 per cent when a 0.5 per cent solution 
of papain is allowed to stand sixteen hours at a temperature of 
15° C. This proves that the decrease in activity for curve 4 
is due to the decomposition of the enzyme, probably by autol- 
ysis, and not by the removal of a co-enzyme. 
“Mr. A. H. Wells, chief of the division of organic chemistry: of the 
Bureau of Science, kindly furnished us with two samples, one sundried 
and the other alcohol precipitated. The latter was practically white. 
The alcohol-precipitated sample showed the greater digestive powers. 
