| Role of Enzymes in Nutrition |
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Enzymes are chemical substances produced in the living organism. They are
marvellous organic catalysts which are essential to life as they control all the
chemical reactions that take place in a living system. Enzymes are part of all
living cells, including those of plants and animals.
The term enzyme, which literally means in yeast’, was coined following the
demonstration of catalytic properties of yeast and yeast juices. Although
enzymes are produced in the living cell, they are not dependent upon the vital
processes of the cell and work outside the cell. Certain enzymes of yeast, for
instance, when expressed from the yeast cells are capable of exerting their
usual effect, that is, the conversion of sugar to alcohol.
A striking feature of enzymes is that while they enter into chemical reaction,
they remain intact in the process. They however, act with maximum efficiency at
a certain temperature. Lowering the temperature below or raising it above this
level slows the reaction. A high degree of heat, that is above 60 o C,
permanently destroys their action.
It has been estimated that there are over 20,000 enzymes in the human body. This
estimate is based on the number of bodily processes that seem to require action.
However, so far only about 1,000 enzymes have been identified. But their great
role in nutrition and other living processes has been firmly established. They
are protein molecules made up of chains of amino acids. They play a vital role
and work more efficiently than any reagent concocted by chemists. Thus for
instance, a chemist can separate proteins into their component amino acids by
boiling them at 166 o C for over 18 hours in a strong solution of hydrochloric
acid, but the enzymes of the small intestines can do so in less than three hours
at body temperature in a neutral medium.
A feature which distinguishes enzymes from inorganic catalysts is that they are
absolutely specific in their actions. This means that a particular enzyme can
cause reactions involving only a particular type of substance or a group of
closely related substances. The substance on which the enzyme acts is known as
"substrate". The specificity of an enzyme is, however, related to the
formation of the enzyme-substrate complex which requires that the appropriate
groupings of both substrate and enzyme should be in correct relative position.
The substrate must fit the enzyme like a key fits its lock.
Enzymes which are used in the cells which make them are called intracellular
enzymes. Enzymes which are produced in cells which secrete them to other parts
of the body are known as extracellular enzymes. Digestive juices are an example
of the latter type. Nomenclature
There are few enzymes whose names have been established by long usage such as
ptyalin, pepsin, trypsin and erepsin. Apart from these, enzymes are usually
named by adding the suffixes to the main part of the name of the substrate upon
which they act. Thus amylases act upon starch (amylum), lac- tase acts upon
lactose, lipases act upon lipids, maltase acts upon maltose and protesses act
upon lipids, maltase acts upon maltose and protesses act upon proteins. There
are, however, several enzymes which act upon many substances in different ways.
These enzymes are named by their functions rather than substrates. Thus, an
enzyme which causes deamination's is called a deaminase and oxidising enzyme an
oxidase.
Some enzymes work efficiently only if some other specific substance is present
in addition to substrate. This other substance is known as an
"activator" or a "coenzyme" . "Acti- vators" are
usually inorganic ions. They increase the activity of a complete enzyme and may
take part in the formation of the enzyme-substrate complex. Many of the coenzymes
are related to vitamins. This explains why vitamin deficiencies
profoundly alter metabolism. Thus, for instance, thiamine, as thiamine
pyrophosphate, functions as a coenzyme in at least 14 enzymes systems. Coenzymes, like enzymes, are being continuously regenerated in the cells.
Enzymes play a decisive role in the digestion of food as they are responsible
for the chemical changes which the food undergoes during digestion. The chemical
changes comprise the breaking up of the large molecules of carbohydrates, fats
and proteins into smaller ones or conversion of complex substances into simple
ones which can be absorbed by the intestines. They also control the numerous
reactions by which these simple substances are utilized in the body for building
up new tissues and producing energy. The enzymes themselves are not broken down
or changed in the process. They remain as powerful at the end of a reaction as
they were at the beginning. Moreover, very small amounts can convert large
amounts of material. They are thus true catalysts.
The process of digestion begins in the mouth. The saliva in the moth, besides
helping to masticate the food, carries an enzyme called ptyalin which begins the
chemical action of digestion. It initiates the catabolism (breakdown) of
carbohydrates by converting starches into simple sugars. This explains the need
for thorough mastication of starchy food in the mouth. If this is not done the
ptyalin cannot carry out its functions as it is active in an alkaline, neutral
or slightly acid medium and is inactivated by the highly acid gastric juices in
the stomach.
Although enzymatic action starts while food is being chewed, digestion moves
into high gear only when the chewed food has passed the esophagus and reached
the stomach. While the physical action of peristalsis churns and kneads solid
food into a semi-solid amorphous mixture called chyme, this mixture undergoes
chemical changes initiated by gastric juices secreted by the walls of the
stomach. These juices include mucus for lubricating the stomach, hydrochloric
acid and gastric juice. The enzyme or active principle of the gastric juice is
pepsin. This enzyme in combination with hydrochloric acid starts the breakdown
of proteins into absorbable amino acids called polypeptides. An additional
enzyme, rennin, plays an important role in the stomach of the infant. It curdles
milk and allows the pepsin to work upon it. The gastric juice has no effect upon
starches or fats.
When the chyme leaves the stomach and enters the small intestine through the
pylorus - the lower escape valve, it still contains much food which is in the
form of raw material not yet ready for absorption in the body. Digestion is
completed inside the small intestine by several juices. From liver comes a
liquid called bile which converts fat globules into a smooth emulsion.
The pancreas contributes various enzymes which continue the breakdown of
proteins, help to divide starch into sugars and work with bile in digesting
fats. The small intestine itself secretes enzymes from its inner wall to
complete the reactions. When all the enzymes have done their work, the food is
digested and rendered fit for absorption by the system.
Enzymes form part of the food we eat. Raw foods contain enzymes in abundance;
cooking, pasteurising, pickling, smoking and other processings denature enzymes.
It is, therefore, essential to include in our diet, substantial amount of raw
foods in the form of fruits, raw salads and sprouts. Studies have revealed that
the body without sufficient raw materials from raw foods, may tire and produce
fewer enzymes year after year. This may lead to wearing out of body processes
and consequent worn-out looks.
Thanks to the Health
Library for this information.
AN IMPORTANT NOTE: The information on this page is
not in any way offered as prescription, diagnosis nor treatment for any disease,
illness, infirmity or physical condition. Any form of self-treatment or
alternative health program necessarily must involve an individual's acceptance
of some risk, and no one should assume otherwise.
Persons needing medical care should consult a doctor or physician before making
any health decision
Kevin James Rogers
Director
Nivek Nywnorb Sregor & Co Pty Ltd
trading as:
Retsel Australia & GrainMaster Australian Whisper Mill Distributors
P.O. Box 712,
Dandenong, Vic 3175
Australia
Telephone (03) 9795 2725 or mobile (0414) 95 2725
Fax (03) 9713 2622
International phone (61 3) 9795 2725 or mobile (61 414) 95 2725
International fax (61 3) 9713 2622
E-mail kevinjamesrogers@bigpond.com
Web sites: http://www.retsel.com.au -
http://www.grainmaster.com.au