An antioxidant is a molecule that inhibits the oxidation of
other molecules. Oxidation is a chemical reaction involving the loss of electrons or an
increase in oxidation state. Oxidation reactions can produce free radicals. In turn,
these radicals can start chain
reactions. When the chain reaction occurs in a cell, it can cause damage or death to the cell. Antioxidants
terminate these chain reactions by removing free radical intermediates, and
inhibit other oxidation reactions. They do this by being oxidized themselves,
so antioxidants are oftenreducing agents such
as thiols, ascorbic acid (vitamin C), or polyphenols.
Although oxidation reactions are
crucial for life, they can also be damaging; plants and animals maintain
complex systems of multiple types of antioxidants, such as glutathione and vitamin-vitamin as well as enzymessuch as catalase, superoxide dismutase and
various peroxidases. Insufficient levels of
antioxidants, or inhibition of the
antioxidant enzymes, cause oxidative stress and may damage or kill cells. Oxidative
stress is damage to cell structure and cell function by overly reactive
oxygen-containing molecules and chronic excessive inflammation. Oxidative
stress seems to play a significant role in many human diseases, including
cancers. The use of antioxidants inpharmacology is intensively studied, particularly as
treatments for stroke andneurodegenerative diseases.
For these reasons, oxidative stress can be considered to be both the cause and
the consequence of some diseases.
Antioxidants are widely used in dietary supplements and
have been investigated for the prevention of diseases such as cancer, coronary heart disease and altitude sickness. Although initial studies suggested
that antioxidant supplements might promote health, later large trials including of beta-carotene, vitamin A, and vitamin
E singly or in different combinations suggest that supplementation has no
effect on mortality or possibly increases it. Randomized trials of taking
antioxidants including beta carotene, vitamin and selenium have
shown no effect on cancer risk or have increased cancer risk. Supplementation
with selenium or vitamin E does not reduce the risk of cardiovascular disease
Antioxidants also have many industrial
uses, such as preservatives in food and cosmetics
and to prevent the degradation of rubber and gasoline.
Glutathione is
a cysteine-containing peptide found
in most forms of aerobic life It is not required in the diet and is instead
synthesized in cells from its constituentamino
acids.[ Glutathione has antioxidant
properties since the thiol group
in itscysteine moiety is
a
reducing agent and can be reversibly oxidized and reduced. In cells,
glutathione is maintained in the reduced form by the enzyme glutathione reductase and
in turn reduces other metabolites and enzyme systems, such as ascorbate in the glutathione-ascorbate cycle, glutathione peroxidases and glutaredoxins,
as well as reacting directly with oxidants. Due to its high concentration and its
central role in maintaining the cell's redox state, glutathione is one of the
most important cellular antioxidantsIn some organisms glutathione is replaced
by other thiols, such as by mycothiol in
the Actinomycetes, bacillithiol in
some Gram-positive bacteria, or by trypanothione in
the Kinetoplastids.
The glutathione system
includes glutathione, glutathione reductase, glutathione peroxidases and glutathione S-transferases.
This system is found in animals, plants and microorganisms. Glutathione peroxidase is an enzyme
containing four selenium-cofactors that
catalyzes the breakdown of hydrogen peroxide and organic hydroperoxides. There
are at least four different glutathione peroxidase isozymes in
animals Glutathione peroxidase 1 is the most abundant and is a very efficient
scavenger of hydrogen peroxide, while glutathione peroxidase 4 is most active
with lipid hydroperoxides. Surprisingly, glutathione peroxidase 1 is
dispensable, as mice lacking this enzyme have normal lifespans, but they are hypersensitive to induced
oxidative stress. In
addition, the glutathione S-transferases show
high activity with lipid peroxides. These
enzymes are at particularly high levels in the liver and also serve indetoxification metabolism.
A part of Glutathione Testimoni |
Read more
information about Glutathione @
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