Vines. — The Proteases of Plants (IV). 
121 
Summary. . 
The facts established by the foregoing experiments are briefly these : — 
(1) The ungerminated seeds were found to contain a protease which 
acted (a) immediately on Witte-peptone, and (b) more or less slowly on the 
reserve proteids of the seeds : 
( 2 ) The germinated seeds were found to contain a protease that 
digested fibrin : this protease was also found in certain cases (Pea, Lupin, 
Maize) to be slowly developed in the substance of the ungerminated seed in 
the course of the experiment. 
The object of this research was to obtain, from the study of seeds, 
evidence bearing upon the conclusion at which I had arrived (5) as the result 
of experiments with Yeast, Malt, Mushroom, and other vegetable substances, 
that, in those cases in which fibrin-digestion takes place, two proteases are 
present : the one, essentially peptolysing, ereptase, the other essentially 
peptonizing, peptase as I believe. The conclusion was based mainly on 
observations showing that by appropriate chemical means, such as variations 
in the reaction of the liquid, it is possible to induce differential effects, to 
retard or inhibit the one process without similarly (if at all) interfering with 
the other. It is, I consider, definitely supported by the results stated 
above, which afford evidence of a new kind — the separation of the proteases 
in point of time. Thus, in the ungerminated seed, one protease only, 
ereptase, was found to be present, to begin with : no evidence of the 
presence of the fibrin-digesting protease could be obtained until several 
days after the experiment had proceeded or germination had been going on. 
It must, however, be admitted that all the evidence that I have 
accumulated does not yet suffice to prove that there is no such thing as 
‘ vegetable trypsin.’ One point, at any rate, has become clear, namely, 
that ‘ vegetable trypsin ’ is a mixture of enzymes and that ereptase is one 
of the constituents. But the nature of the other constituent (or constituents), 
the fibrin-digesting protease, remains uncertain : it may be a tryptase, but 
it may also be a peptase. It is not, I think, going too far to suggest that 
the known facts make the latter suggestion the more probable : to transfer, 
in fact, the onus probandi to those who hold that the enzyme in question is 
a tryptase. 
The general course of proteolysis in the germinating seed can now be 
intelligibly followed. At first it is confined to the action of the ereptase 
upon the more digestible reserve proteids such as the proteoses. Within 
a few days after germination has begun, the fibrin-digesting enzyme is 
developed : this hydrolyses the higher proteids of the seed, and so produces 
material upon which the ereptase can continue to act. There does not 
seem to be any reason whatever for the assumption of the direct interven- 
tion of the protoplasm in the process. 
