Malate dehydrogenase

Definition

Malate dehydrogenase is an enzyme that catalyzes the conversion of malate to oxaloacetate, a key step in the citric acid cycle. This reaction is crucial because it helps regenerate oxaloacetate, allowing the cycle to continue and ultimately contributing to the production of energy in the form of ATP. It also plays a role in the interconnected metabolic pathways of cellular respiration and energy production.

5 Must Know Facts For Your Next Test

1. Malate dehydrogenase uses NAD+ as a cofactor, converting it to NADH during the oxidation of malate to oxaloacetate.
2. There are two forms of malate dehydrogenase: mitochondrial and cytosolic, each localized in different parts of the cell and involved in different aspects of metabolism.
3. The reaction catalyzed by malate dehydrogenase is reversible, which allows it to play a role in both the citric acid cycle and gluconeogenesis.
4. Malate dehydrogenase activity is regulated by substrate availability and the cellular energy state, helping maintain metabolic balance.
5. The enzyme is vital for maintaining the flow of intermediates in the citric acid cycle, which is crucial for aerobic respiration and overall cellular energy production.

Review Questions

• How does malate dehydrogenase contribute to the continuity of the citric acid cycle?
  • Malate dehydrogenase plays a crucial role in the citric acid cycle by catalyzing the conversion of malate to oxaloacetate. This reaction regenerates oxaloacetate, which is necessary for the cycle to continue. If malate dehydrogenase were not functioning, the accumulation of malate would prevent the cycle from proceeding, ultimately affecting energy production in the cell.
• Discuss how malate dehydrogenase connects cellular respiration with other metabolic pathways.
  • Malate dehydrogenase connects cellular respiration with other metabolic pathways by participating in both the citric acid cycle and gluconeogenesis. By facilitating the reversible conversion between malate and oxaloacetate, this enzyme enables cells to shift between energy production and glucose synthesis based on metabolic demands. This adaptability is essential for maintaining energy homeostasis within the cell.
• Evaluate the significance of NAD+ in the function of malate dehydrogenase and its broader implications for cellular metabolism.
  • NAD+ is vital for the function of malate dehydrogenase as it serves as a cofactor that accepts electrons during the oxidation of malate. The conversion of NAD+ to NADH during this reaction not only fuels further reactions in cellular respiration but also links redox reactions with energy metabolism. The availability of NAD+ can influence cellular metabolic pathways, impacting overall energy balance and highlighting its critical role in maintaining cellular health and function.

Related terms

Citric Acid Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Oxidative Phosphorylation: The metabolic pathway that uses energy released by the electron transport chain to power the synthesis of ATP from ADP and inorganic phosphate.

NAD+: Nicotinamide adenine dinucleotide, a coenzyme that acts as an electron carrier in various metabolic reactions, including those catalyzed by malate dehydrogenase.