Glutamate dehydrogenase

Definition

Glutamate dehydrogenase is an important enzyme that catalyzes the reversible conversion of glutamate to alpha-ketoglutarate while reducing NAD+ to NADH or oxidizing NADPH to NADP+. This enzyme plays a crucial role in amino acid metabolism, linking amino acid biosynthesis with catabolism and contributing to nitrogen metabolism and the urea cycle.

5 Must Know Facts For Your Next Test

1. Glutamate dehydrogenase exists in two forms, one that uses NAD+ as a cofactor for oxidation and another that uses NADPH for reduction, reflecting its versatility in different metabolic contexts.
2. This enzyme is predominantly found in the mitochondria of cells, where it contributes to energy production and amino acid regulation.
3. Glutamate dehydrogenase plays a significant role in the integration of nitrogen from amino acids into the urea cycle, thus facilitating the removal of excess nitrogen from the body.
4. The activity of this enzyme is regulated by various factors, including the concentrations of ATP, ADP, GTP, and GDP, which reflect the energy state of the cell.
5. Mutations in the gene encoding glutamate dehydrogenase have been linked to metabolic disorders, highlighting its importance in maintaining amino acid and nitrogen homeostasis.

Review Questions

• How does glutamate dehydrogenase link amino acid catabolism to energy production?
  • Glutamate dehydrogenase links amino acid catabolism to energy production by converting glutamate into alpha-ketoglutarate, a key intermediate in the Krebs cycle. This conversion not only releases energy but also helps maintain a balance between amino acid levels and energy metabolism. By facilitating this transformation, glutamate dehydrogenase ensures that excess amino acids can be used efficiently for energy when needed.
• In what ways does glutamate dehydrogenase contribute to the regulation of nitrogen levels in the body?
  • Glutamate dehydrogenase contributes to nitrogen regulation by facilitating the deamination of glutamate, producing alpha-ketoglutarate and releasing ammonia. The ammonia generated can then enter the urea cycle, where it is converted into urea for excretion. This process helps prevent toxic accumulation of ammonia in the body and is essential for maintaining nitrogen balance.
• Evaluate how fluctuations in ATP and ADP concentrations might influence the activity of glutamate dehydrogenase during metabolic stress.
  • Fluctuations in ATP and ADP concentrations significantly influence the activity of glutamate dehydrogenase during metabolic stress. When ATP levels are high and ADP levels are low, this typically signals an energy-rich state, leading to decreased enzyme activity as there is less need for energy generation from amino acids. Conversely, during metabolic stress when ATP is low and ADP is high, enzyme activity may increase to enhance the conversion of glutamate into alpha-ketoglutarate, promoting energy production and compensating for reduced ATP availability. This regulatory mechanism ensures that cellular energy demands are met under varying conditions.

Related terms

Alpha-ketoglutarate: A key intermediate in the Krebs cycle that can be derived from glutamate through deamination, playing a critical role in energy production and amino acid metabolism.

NADH:

A reduced form of nicotinamide adenine dinucleotide that serves as an electron carrier in cellular respiration, playing a crucial role in energy metabolism.

Urea cycle: A series of biochemical reactions that convert ammonia to urea for excretion, helping to regulate nitrogen levels in the body and prevent toxicity.