- Laboratory Report on Succinate Dehydrogenase (SDH). Illust...
Laboratory Report on Succinate Dehydrogenase (SDH). Illustrate your essay with specific examples.
Succinate dehydrogenase or SDH is a vital component in the
tricarboxylic acid cycle (TCA) or Krebs cycle (1,2,3). As an
important enzyme in the Kreb's cycle, succinate dehydrogenase
oxidizes succinate to fumarate (1,2). Purification of this enzyme
is difficult but it has been isolated from organisms such as
Bacillus subtilis, E. coli where it presents itself as one of the
transmembrane proteins of these organisms (4). It has also been
likewise detected and isolated from Rhodospirillum rubrum (4).
However, in both mammal and animal tissues, SDH has been purified
and the enzyme's properties in both tissues were seen to be
identical (5). Analysis of the structure of SDH (5,6) from those
isolated in E. coli revealed that it has two large polypeptide
subunits (64.3 kDa and 26 kDa) and two smaller subunits (14.2 kDa
and 12.8 kDa) (4, 7). These larger subunits act as the active sites
of SDH (7) while the smaller subunits were discovered to be
hydrophobic and are attached to the cell membrane of the E. coli
(8,9). SDH is unique due to the fact that in the Kreb's cycle, it
is the only single enzyme that is found to be bound to the
mitochondria's inner membrane (8, 9, 10). Existing as a component
of complex II in the electron transport chain (10, 11) it functions
as a transporter of electrons to uniquinone-10 from
Owing to its importance, it is necessary to be identify and
follow laboratory procedures that would elucidate its presence in a
mammalian tissue. For this purpose, this laboratory exercise will
seek to demonstrate the presence of succinate dehydrogenase in a
muscle tissue of a rat.
Revealing the presence of SDH in a muscle tissue indicates that
these tissues have abundant mitochondria (13) compared to other
tissues that do not use up as much energy. Meanwhile,
quantification of SDH is also vital in determining whether there is
an overproduction of superoxides that will lead to formation of
tumors in humans. As Rustin, P and his colleagues expressed, "SDH
plays a specific role in the handling of oxygen in mitochondria"
(14). This group of researchers explained that SDH, when it is
unable to perform its function in reducing the pool of ubiquinones,
can lead to condition where cells and tissues are unable to resist
the stress caused by oxygen toxicity. As presented in their
research paper (14), SDH not only plays an important role in the
Kreb's cycle and electron transport chain but also serves as an
antioxidant enzyme. On the other hand, SDH can also be used in the
succinate dehydrogenase inhibition (SDI) test for predicting the
heat sensitivity of tumor tissues (14). SDI test will show whether
malignant or tumor tissues can be effectively treated with
hyperthermia (14, 15).
This experiment is integral in understanding the presence and
role of SDH in tissues of animals and humans. In tissues that are
highly active, SDH would be present in higher quantities as
compared to tissues that are less active and need less energy to
carry out their functions. Generally, quantifying SDH would also
reveal if there is an abnormality in its production and abundance.
For example, in tumor lesions, when SDH is unable to reduce the
level of ubiquinones normally, it may lead to inability of tissues
and cells to handle oxidative stress. In malignant tissues, the SDI
test is also used as a reliable tool to indicate whether these
lesions will respond to hyperthermia- one of the important
therapies used to treat or contain malignant tissues.