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ENZYMES. 61
j-=7T =K (page 32). It follows that the same equilibrium is attained irrespective
of whether we start with alcohol+acid, or ester+H20. The equilibrium is also
independent of the antecedents as well as the quantity of enzyme.
On comparing the equilibrium constants (A’) which are obtained with dif-
ferent quantities of ester or acid, it is shown that in the above equation V(7s
must be introduced instead of Ce in order to obtain constant values for A’. In
the saponification of the ester the reaction velocity is proportional to \^Cs,
and not Ce. According to Dietz this is due to the fact that the system is a
heterogeneous one, and that only that part of the ester which is absorbed by
the solid phase (enzyme) takes part in the reaction. The velocity constant of
the ester formation is shown to be proportional to the quantity of enzyme.
According to what was stated above (page 35), the equilibrium in a reversible
reaction must be independent of the nature of the catalyst. This was not the
case in Dietz’s experiments. With picric acid as the catalyst a different equilib-
rium was obtained than with the pancreas enzyme. With the acid as catalyst
the equilibrium was moved toward the direction of the ester. While this action
is not understood it may perhaps be explained by the fact that the system in one
case was homogeneous and in the other case heterogeneous.
Similar observations that the enzymotic end-condition can be different from
the stabile end-condition of the same system have previously been made by
Tammann, 1
but in these cases generally so-called false equilibrium existed, which
for example, by the addition of more enzyme changed, so that the cleavage pro-
ceeds further. These false equilibria are generally caused by the enzyme being
destroyed or put out of action in other ways.
Among the enzymotic-ester syntheses we must also include! he or-
mation of carbohydrate phosphoric acid ester in fermenting sugar solu-
tions in the presence of soluble phosphates, as first observed by Harden
and Young.2
These will be discussed in detail in Chapter III.
It is seen that enzymotic syntheses are known. From this it fol-
lows that the questionable enzyme reactions are to be considered as
reversible. In certain cases another substance which cannot be split
by the enzyme is formed while in other cases the opposite direction of the
reaction can be detected by means of various constituents of the same
enzyme solution.
Specificity of Enzyme Action. It has been known for a long time
that a great difference exists in regard to the action of enzymes in the
sense that different enzymes act only upon certain classes of bodies (pro-
teins, carbohydrates, fats). Then there also exist differences in the
manner in which different enzymes of the same group influence different
members of the same class (maltase, lactase, saccharase). Finally, it is
possible for one enzyme to attack one of two optical antipodes and the
other not at all, or only to a slight degree. That optical antipodes
are burned with unequal facility in the organism was shown by E. Fischer,
and that of the numerous aldohexoses only three, rf-glucose, d-mannose
1
Zeitschr. f. physiol. Chem., 16, 271 (1892).
2
Proc. Roy. Soc. B, 1908 p. 209.
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