True about glutamate dehydrogenase –
**Core Concept**
Glutamate dehydrogenase (GDH) is a key enzyme involved in the metabolism of glutamate, catalyzing the conversion between glutamate and α-ketoglutarate through an NAD+ or NADP+ dependent reaction. This enzyme plays a crucial role in nitrogen metabolism, particularly in the brain, where it helps regulate glutamate levels.
**Why the Correct Answer is Right**
The correct answer involves the unique aspect of GDH, which is its ability to utilize both NAD+ and NADP+ as cofactors. This dual cofactor property allows GDH to function in both the catabolic and anabolic pathways of glutamate metabolism. In the brain, GDH is predominantly involved in the catabolic pathway, where it helps to break down glutamate to α-ketoglutarate, producing NADH in the process.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the cofactor specificity of GDH. While GDH can utilize both NAD+ and NADP+, it is not exclusively dependent on either cofactor.
**Option B:** This option is incorrect because it does not accurately describe the primary function of GDH in the brain. While GDH is involved in glutamate metabolism, its primary role is not in the synthesis of glutamate from α-ketoglutarate.
**Option C:** This option is incorrect because it does not accurately describe the cellular localization of GDH. While GDH is found in various tissues, its primary localization is not in the mitochondria.
**Clinical Pearl / High-Yield Fact**
GDH is a key enzyme involved in the regulation of glutamate levels in the brain, and its dysregulation has been implicated in various neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease.
**Correct Answer:** D