Amylase is 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 pancreatic amylase, sometimes called amylopsin. The
amylase of malt digests barley starch to the disaccharides that are
attacked by yeast in the fermentation process.
Enzymes are a class of
proteins which catalyse chemical reactions. Unlike non-biological 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 40°C 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 times the rate of the un-catalysed 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 carbohydrates.
The Importance of Carbohydrates
Carbohydrates in 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 sugars.
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.
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