convenient to make an actual quantitative
determination of the amount of end-products produced in a given time, as in
the inversion of cane sugar, the hydrolysis of maltose, etc., but such
determinations necessarily involve the removal of some of the reaction
mixture for the purposes of the determinations, and are not, therefore,
suitable for the study of the progressive development of the reaction which
is being studied.

Enzymes are found in all parts of the animal organism and those which are
active in the digestion of food, the metabolism of digested material, the
coagulation of blood, etc., have been extensively studied. A discussion of
these animal enzymes would be out of place in such a text as this, however,
and the following list includes only enzymes which are known to occur in
plant tissues. These well-known enzymes will serve as examples of the
several general types which have thus far been isolated and studied.

------------------- -+-----------+-------------+-------------+-----------
Class and Type. | Enzyme. | Substrate. |End-products.| Found in.
---------------------+-----------+-------------+-------------+-----------
I. Hydrolases | | | |
(_a_) Esterases |Lipase |Fats |Glycerol and |Oily seeds
| | |fatty acids |
| | | |
(_b_) Carbohydrases |Sucrase or |Sucrose |Glucose and |Yeasts
|invertase | |fructose |
| | | |
|Maltase |Maltose and |Glucose, etc.|Barley malt
| |all [alpha]- | |
| |glucosides | |
| | | |
|Dextrinase |Dextrin |Maltose |Malt
| | | |
|Inulase |Inulin |Fructose |Artichokes,
| | | |etc.
| | | |
|Amylase or |Starch |Maltose |Malt, etc.
|diastase | | |
| | | |