Glutamate dehydrogenase in mitochondria is activated by:
**Core Concept**
Glutamate dehydrogenase (GLDH) is a mitochondrial enzyme that catalyzes the reversible reaction between glutamate and α-ketoglutarate. This enzyme plays a crucial role in nitrogen metabolism, linking the amino acid pool with the Krebs cycle.
**Why the Correct Answer is Right**
GLDH is activated by an increase in the concentration of its substrate, glutamate, or its product, α-ketoglutarate. The enzyme is also activated by an increase in the concentration of ATP, which is a regulatory molecule that signals a high energy state in the cell. This activation is achieved through the allosteric binding of ATP to the enzyme, which enhances its activity. Additionally, GLDH is inhibited by NADH, which is a product of the reaction catalyzed by the enzyme. This inhibition is a negative feedback mechanism that prevents excessive production of α-ketoglutarate.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a known activator of GLDH.
* **Option B:** This option is not a known activator of GLDH.
* **Option D:** This option is not a known activator of GLDH.
**Clinical Pearl / High-Yield Fact**
Glutamate dehydrogenase is a key enzyme in the regulation of nitrogen metabolism, and its activity is influenced by the concentration of its substrates and products. In clinical practice, elevated levels of GLDH in the blood can indicate liver or kidney damage, as these organs contain high concentrations of the enzyme.
**Correct Answer:** A. ATP