Isocitrate dehydrogenase

Definition

Isocitrate dehydrogenase is an enzyme that plays a crucial role in the citric acid cycle (Krebs cycle), catalyzing the conversion of isocitrate into alpha-ketoglutarate while producing NADH and releasing carbon dioxide. This enzyme is essential for cellular respiration, as it contributes to energy production and the regulation of metabolic pathways, linking carbohydrate and fat metabolism.

5 Must Know Facts For Your Next Test

1. Isocitrate dehydrogenase exists in two main forms: NAD+-dependent and NADP+-dependent, each playing different roles in metabolic pathways.
2. The enzyme helps regulate the flow of metabolites through the citric acid cycle, influencing energy production based on cellular needs.
3. Mutations in isocitrate dehydrogenase have been linked to various cancers, highlighting its importance in both metabolism and cell regulation.
4. The reaction catalyzed by isocitrate dehydrogenase is irreversible, making it a key regulatory step in the citric acid cycle.
5. In addition to its role in energy production, isocitrate dehydrogenase is involved in biosynthetic pathways, including the synthesis of amino acids and fatty acids.

Review Questions

• How does isocitrate dehydrogenase influence energy production during cellular respiration?
  • Isocitrate dehydrogenase influences energy production by catalyzing the conversion of isocitrate into alpha-ketoglutarate while generating NADH. This reaction not only helps to drive the citric acid cycle forward but also contributes to the overall electron transport chain, where NADH will be further oxidized to produce ATP. By regulating this step, isocitrate dehydrogenase ensures that cells can efficiently respond to their energy demands based on substrate availability and metabolic state.
• Discuss the significance of mutations in isocitrate dehydrogenase and their implications for human health.
  • Mutations in isocitrate dehydrogenase can lead to abnormal metabolic pathways that are associated with various forms of cancer. These mutations often result in a gain of function that alters metabolic processes, promoting tumorigenesis by increasing the levels of certain metabolites. This change can impact cell growth and survival, demonstrating how crucial this enzyme is not just for metabolism but also for maintaining normal cellular functions. Understanding these mutations can provide insights into potential therapeutic targets for cancer treatment.
• Evaluate the role of isocitrate dehydrogenase in both energy production and biosynthetic pathways within cells.
  • Isocitrate dehydrogenase serves a dual purpose in cellular metabolism by participating in both energy production through the citric acid cycle and various biosynthetic pathways. In energy production, it catalyzes a key reaction that contributes to generating NADH, essential for ATP synthesis during oxidative phosphorylation. Simultaneously, it plays a critical role in supplying intermediates like alpha-ketoglutarate for amino acid and fatty acid synthesis. This versatility underscores the enzyme's importance not only for fueling cellular processes but also for maintaining metabolic balance and supporting cell growth 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.

NADH:

A coenzyme that acts as an electron carrier in cellular respiration, playing a key role in the transfer of energy through redox reactions.

Alpha-ketoglutarate: A key intermediate in the citric acid cycle that is formed from isocitrate and is involved in amino acid synthesis and energy production.