an enzyme having physiological, commercial, and historical
significance, also called diastase. It is found in both plants and
animals. Amylase was purified (1835) from malt by Anselme
Payen and Jean Persoz. Their work led them to suspect that similar
substances, now known as enzymes, might be involved in biochemical
processes. Amylase hydrolyzes starch, glycogen, and dextrin to
form in all three instances glucose, maltose, and the limit-dextrins.
Salivary amylase is known as ptyalin; although humans have
this enzyme in their saliva, some mammals, such as horses, dogs, and
cats, do not. Ptyalin begins polysaccharide digestion in the mouth;
the process is completed in the small intestine by the
sometimes called amylopsin. The amylase of malt digests barley starch to the
disaccharides that are attacked by yeast in the fermentation
Enzymes are a class of
proteins which catalyse chemical reactions. Unlike nonbiological
catalysts such as charcoal and platinum, which often need harsh
extremes of temperature and pH, enzymes must work in the mild
conditions of a cell in the body, at approximately 40oC and at a pH
between 6.5 and 7.5. When compared with inorganic catalysts, enzymes
are different in their rate of reaction (often 106 to 1012 the rate
of the uncatalysed reaction) and in their specificity, their ability
to act selectively on a small group of chemically similar substances.
Chemicals changed by enzyme-catalysed reactions are called the
substrates of that enzyme, and they fit into the active site of the
enzyme, where the reaction takes place, in a lock-and-key mechanism.
The products of the reaction then leave the active site, freeing it
up for more similar reactions to take place.
Carbohydrates are one of the three major food
groups needed for proper nutrition. Amylase is the digestive enzyme needed to digest
The Importance of
food are an important and immediate source of energy for the body. Starch
refers to carbohydrates found in plants (grains). Vegetables and fruits are
a source of starch and are broken down to sugar or glucose. Carbohydrates
are present in at least small quantities in most food, but the chief
sources are the sugars and the starches.
- Sugars include
granulated sugar, maple sugar, honey and molasses.
- Simple sugars
are fructose and fruit sugar.
- Double sugars
are sugar cane, sugar beet, maltose or malt sugar, lactose or milk
sugar. All ripe fruits and vegetables contain some natural
- Starches are
present in such foods as rice, wheat and potatoes.
Carbohydrates may be
stored in the body as glycogen for future use. If they are eaten in
excessive amounts, however, the body changes them into fats and stores them
in that form.
If carbohydrates are
not properly broken down before they are absorbed, serious health
consequences can occur.