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54 GENERAL AND PHYSICO-CHEMICAL.
sugar and of starch. Abderhalden and his co-workers have shown
that the parenteral introduction of protein or peptone gives the blood
serum of the animal the power of splitting proteins, which power is
destroyed on heating to 60-65° C.1
The introduction of very large quan-
tities of sugar or proteins per os (over feeding) has the same effect as
the parenteral introduction. Abderhalden considers the active sub-
stances thus obtained as enzymes. The question is still undecided whether
the substances introduced bring about a formation of the enzymes or
whether they only transport the already formed enzymes to the blood.
Heat Production. The question whether in the hydrolytic processes
with the aid of enzymes heat is given off or taken up has been attacked
in two different ways. Grafe 2
could not find either any setting free or
taking up of heat in the digestion of protein in a Rubner calorimeter.
On the other hand Hari 3
by determining the calorific values of albumin
before and after digestion came to about the same results. If we exclude
the work developed in the process then it follows that the energy supply
of the organism is not perceptibly changed by the hydrolytic cleavages
of the protein. The chief source of energy is to be sought in the oxida-
tion processes that follow the cleavages.
Modes of Action of the Enzymes. The enzjr
mes do not suffer any
appreciable change during the reaction they perform, and insignificant
amounts of the enzyme are able to decompose relatively enormous amounts
of the substrate. For example, 1 part of saccharase can invert 100,000
parts of cane-sugar (O’Sullivan and Thompson)4
and 1 part of rennin
can decompose more than 400,000 parts of casein (Hammarsten) 5 .
For these reasons the enzymes have for a long time been considered as
catalytic substances. Nevertheless the enzyme reactions always take
place in heterogeneous media where on one hand the enzyme exists as
colloid and on the other the substrate in many cases is a colloid (starch,
proteins). As above mentioned, the enzymotic decompositions are
often complicated by their taking place over several intermediary steps
to the final product. As indicated by several conditions, the enzymes
also, before they act upon the substrate, combine therewith in some way
or another. The fact that the action of an enzyme is dependent upon the
stereometric construction (page 61) of the substrate speaks essentially
for this view. The substrate also protects certain enzymes against destruc-
»
Ibid., 61, 200; 62, 120, 243 (1909); 64, 100, 423, 426, 427; 66, 88; 69, 23 (1910);
71, 110, 307, 385 (1911). See also 77, 250 (1912).
2
Arch. f. Hygiene, 62, 216 (1907).
•ranger’s Arch, 115, 11 (1906); 121, 459 (1908).
* Journ. ohem. Soc, 57, 926 (1890).
6 See Maly’s Jahresber, 7.
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