To ee ee ee eT eee ere ee ee 
1905] DEAN—PROTEOLYTIC ENZYMES 339 
distinct tryptophan tests, that with deutero-proteose B was very faint; 
none of the boiled digestions showed any trace of tryptophan. 
In summing up the results of the experiments described above, 
we may note that evidence of the presence of a protease has been 
obtained in the leaves of the spinach and cabbage, the blossoming 
heads of Daucus Carota and the developing seeds of that plant, in 
the leaves and unripe seeds of the chestnut, the etiolated seedlings 
of Phaseolus Mungo, the seeds and seedlings of Cucurbita maxima, 
and the seeds of Cucurbita Pepo. In the case of Phaseolus vulgaris, 
experiments with all stages of the germination of the seed have shown 
that the cotyledons always contain an enzyme of the erepsin group, 
and at no time can any evidence of the presence of an enzyme 
capable of attacking the proteids of the seed be obtained. This 
€reptase may be removed from the bean extracts by half saturation 
of the solution with ammonium sulphate. On dissolving this precipi- 
tate in water and dialyzing the solution free from sulphates, the 
enzyme is obtained in a solution which is perfectly clear and gives 
but feeble reactions for proteids. A preparation of the enzyme may 
be obtained by drying this solution at a temperature below 50° C. 
The enzyme acts on the proto-proteose, the hetero-proteose, and the 
deutero-proteoses, separated from Witte peptone; it is quite inactive 
on phaseolin of the bean, excelsin of the Brazil nut, edestin of the 
hemp seed, and boiled fibrin. 
There can be no doubt but that the large proteid store in bean 
seeds is utilized in germination, and in all probability this utilization 
is preceded by cleavage to the amido-acids, hexon bases, etc. What 
effects this cleavage, and what part, if any, the ereptase plays, are 
Unsolved problems. It is likewise unknown whether or not this 
®nzyme occurs in other parts of the plant or whether enzymes of the 
trypsin type are present in certain tissues. 
The investigation of which this is a partial report was carried 
Cut with the assistance of a grant from the Carnegie Institution. 
LaBoratory oF PLANT PHysIoLocy, 
SHEFFIELD SCIENTIFIC SCHOOL, 
YALE UNnrversity 
