Why is succinate dehydrogenase a good marker enzyme?

Answer 1

Isolation of any organelle requires a reliable test for the presence of the organelle. Typically, this is done by following the activity of an enzyme that is known to be localized exclusively in the target organelle. Such enzymes are known as marker enzymes. For example, the enzyme acid phosphatase (that cleaves terminal phosphate group from substrates and has a pH optimum in the

acidic range) is localized in lysosomes, while the enzyme succinate dehydrogenase is localized in mitochondria. By monitoring where each enzyme activity is found during a cell fractionationprotocol, one can monitor the fractionation of lysosomes and mitochondria, respectively.

Marker enzymes also provide information on the biochemical purity of the fractionated organelles. The presence of unwanted marker enzyme activity in the preparation indicates the level

of contamination by other organelles, while the degree of enrichment for the desired organelle is determined by the specific activity of the target marker enzyme. Although marker enzymes reveal much concerning the purity of the organelle preparation, electron microscopy is generally used as a

final step to assess the preparation's purity and the morphology of the isolated organelle.

Answer 2

Succinate dehydrogenase is a good marker enzyme because it is a key enzyme in both the citric acid cycle and the electron transport chain of aerobic respiration. It is located in the inner mitochondrial membrane and is essential for the conversion of succinate to fumarate while transferring electrons to the electron transport chain, making it a reliable indicator of mitochondrial function. Additionally, succinate dehydrogenase is often used as a marker for mitochondrial content in tissues or cells due to its association with oxidative metabolism.