Malate Dehydrogenase

Definition

Malate dehydrogenase is a crucial enzyme involved in the citric acid cycle, as well as in the process of gluconeogenesis. It catalyzes the reversible oxidation of malate to oxaloacetate, playing a central role in cellular energy production and carbohydrate metabolism.

5 Must Know Facts For Your Next Test

1. Malate dehydrogenase catalyzes the interconversion of malate and oxaloacetate, which is a key step in the citric acid cycle.
2. The enzyme plays a crucial role in the regulation of the citric acid cycle by controlling the availability of oxaloacetate, an essential substrate for the cycle.
3. In gluconeogenesis, malate dehydrogenase is involved in the conversion of oxaloacetate to phosphoenolpyruvate, a key intermediate in the synthesis of glucose.
4. Malate dehydrogenase is found in both the cytosol and the mitochondria, with the mitochondrial form being primarily involved in the citric acid cycle.
5. The activity of malate dehydrogenase is regulated by various factors, including the availability of its substrates, the redox state of the cell, and the presence of allosteric modulators.

Review Questions

• Explain the role of malate dehydrogenase in the citric acid cycle.
  • Malate dehydrogenase is a crucial enzyme in the citric acid cycle, where it catalyzes the reversible conversion of malate to oxaloacetate. This reaction is essential for maintaining the supply of oxaloacetate, a key substrate for the cycle. By regulating the availability of oxaloacetate, malate dehydrogenase plays a central role in controlling the overall rate and efficiency of the citric acid cycle, which is the primary pathway for the oxidation of acetyl-CoA and the generation of ATP in aerobic organisms.
• Describe the involvement of malate dehydrogenase in the process of gluconeogenesis.
  • In the process of gluconeogenesis, malate dehydrogenase is involved in the conversion of oxaloacetate to phosphoenolpyruvate, a key intermediate in the synthesis of glucose from non-carbohydrate precursors. This reaction is an important step in the gluconeogenic pathway, as it allows the body to maintain blood glucose levels even in the absence of dietary carbohydrates. The activity of malate dehydrogenase, along with other gluconeogenic enzymes, is tightly regulated to ensure the appropriate production of glucose to meet the body's energy needs.
• Analyze the significance of the dual localization of malate dehydrogenase in the cytosol and mitochondria, and how this contributes to its role in cellular metabolism.
  • Malate dehydrogenase is found in both the cytosol and the mitochondria, which allows it to participate in multiple metabolic pathways. The mitochondrial form of the enzyme is primarily involved in the citric acid cycle, where it catalyzes the interconversion of malate and oxaloacetate. The cytosolic form, on the other hand, plays a role in gluconeogenesis by contributing to the conversion of oxaloacetate to phosphoenolpyruvate. This dual localization of malate dehydrogenase enables it to act as a crucial link between the citric acid cycle and gluconeogenesis, allowing the cell to coordinate the production of energy and the synthesis of glucose as needed to maintain metabolic homeostasis.

Related terms

Citric Acid Cycle:

Also known as the Krebs cycle, it is a series of chemical reactions that occur in the mitochondria of cells, converting acetyl-CoA derived from the breakdown of carbohydrates, fats, and proteins into carbon dioxide and energy in the form of ATP.

Gluconeogenesis:

The metabolic pathway that synthesizes glucose from non-carbohydrate precursors, such as amino acids, lactate, and glycerol, allowing the body to maintain blood glucose levels even in the absence of dietary carbohydrates.

Oxaloacetate:

A four-carbon dicarboxylic acid that is an important intermediate in the citric acid cycle and gluconeogenesis, serving as a substrate for malate dehydrogenase.