he enzyme.

The influence of activators, or inhibitors, in providing favorable or
unfavorable conditions for the action of an enzyme, should not be confused
with the relation to the enzyme itself of what are known as "coenzymes" and
"antienzymes," discussed in the following paragraph.

COENZYMES AND ANTIENZYMES

In the cases of many enzymes of animal tissues, it has been found that they
are absolutely inactive unless accompanied by some other substance which is
normally present in the gland, or protoplasm, which secretes them. Thus,
the bile salts are absolutely necessary to the activity of trypsin, in its
characteristic protein-splitting action. Such substances are known as
"coenzymes." They can usually be separated from their corresponding enzymes
by dialysis, the coenzyme passing through the parchment membrane. Such
coenzymes are not killed by boiling the dialyzate, and the activity of the
enzyme is restored by adding the boiled dialyzate to the liquid which
remains within the dialyzer.

The best known example of a coenzyme in plant tissues is in connection with
the activity of the zymase of yeast cells. If yeast juice be filtered
through a gelatin filter, the colloidal enzymes which are left behind are
entirely inactive in producing fermentation, but may be restored to
activity again by mixing with the filtrate. An examination of this
filtrate, which contains the coenzyme for zymase, shows that it contains
soluble phosphates and some other substance whose exact nature has not yet
been determined, both of which are necessary to the activity of the zymase.
The phosphates seem to enter into some definite chemical combination with
the substrate sugars, while the other coenzyme seems to be necessary in
order to make possible the final breaking down of the sugar-phosphate
complex by the zymase. This phenomenon of coenzyme relationship is not very
frequently observed in plant enzyme studies, probably because the coenzyme
(if there be such, in the case which is under observation) usually
accompanies the enzyme itself through the various processes of extraction
and purification of the material for study. However, care must be taken in
all cases when dialysis is employed, to see that a possible coenzyme is not
separated from an otherwise active preparation.

An entirely different type of phenomenon is that exhibited by
"antienzymes." These are found in the various intestinal worms which live
in