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Glutathione, antioxidant defense
and regulation of its synthesis.
I'm Henry J. Forman.
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The organization of
this talk begins with
a description of the role of
glutathione in
protection of cells.
The sources of oxidants and
electrophiles will be described,
followed by examination
of the elimination of
oxidants and other electrophiles
that depends upon glutathione.
The glutathione status
of the cell can
be assessed and methods
will be described for that.
Next, we will describe the
synthesis of glutathione,
beginning with the pathway for
the synthesis and the regulation
of the enzymes in that pathway.
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What is glutathione?
Glutathione which is
abbreviated as GSH,
GSH stands for selfhydro,
is the most important small
molecular antioxidant
synthesized in cells.
It's a tripeptide that's
made from three
amino acids and has
an unusual amide bond between
the gamma-carboxyl group of
glutamate and the amino
group of the cysteine.
The cysteine, which
has the self hydrogen,
is involved in reduction
and conjugation reactions.
Glutathione is involved in
enzyme catalyzed
removal of peroxides
and many xenobiotics and is
involved in cell
cycle regulation.
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The elimination of many
xenobiotic electrophiles can be
accomplished through
conjugation to
glutathione and
excretion from the cell.
The quinone menadione
as shown can react
with glutathione nonenzymatically
to form an adduct.
However, the enzymatic reaction,
which is catalyzed by
a glutathione
S-transferase where
the S stands for
sulfur is much faster.
Once the adduct is
made to a quinone,
such as menadione,
that can rearrange
to form a quinol,
and a quinol is considered to
be less toxic than the quinone.
It also as a conjugate
with glutathione,
is excreted from
the cell through
proteins such as the multi-drug
resistance proteins.
