Transfer of the carbamoyl moiety of carbamoyl phosphate to ornithine is catalysed by a liver mitochondrial enzyme:
**Core Concept**
The transfer of the carbamoyl moiety of carbamoyl phosphate to ornithine is a crucial step in the urea cycle, which occurs primarily in the liver. This process involves the conversion of carbamoyl phosphate to citrulline, catalyzed by a specific enzyme in the mitochondria.
**Why the Correct Answer is Right**
The correct enzyme responsible for this reaction is ornithine transcarbamylase (OTC). OTC is a mitochondrial enzyme that catalyzes the condensation of carbamoyl phosphate and ornithine to form citrulline. This reaction is a key step in the urea cycle, which is essential for the detoxification of ammonia in the body. The enzyme OTC requires magnesium ions as a cofactor to facilitate the transfer of the carbamoyl group from carbamoyl phosphate to ornithine.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the urea cycle or the transfer of the carbamoyl moiety to ornithine.
**Option B:** This option is incorrect because it does not accurately describe the enzyme responsible for the transfer of the carbamoyl moiety to ornithine.
**Option C:** This option is incorrect because it is not a recognized enzyme involved in the urea cycle.
**Clinical Pearl / High-Yield Fact**
Ornithine transcarbamylase (OTC) deficiency is a rare genetic disorder that can lead to hyperammonemia and neurological symptoms. It is essential for medical professionals to recognize the clinical presentation of OTC deficiency and initiate prompt treatment to prevent long-term neurological damage.
**Correct Answer: C. Ornithine transcarbamylase (OTC)**