Question

The presence of arginase confirms that

• A. Urea cycle is operating
• B. Urea cycle may be operating
• C. Arginine is being converted into ornithine
• D. Arginine is being converted into citruline

Answer 1

The correct option is C Arginine is being converted into ornithine

In mammals, urea is produced from ammonia in five enzymatic steps. The urea cycle begins inside liver mitochondria but three of the subsequent steps takes place in the cytosol; the cycle thus spans two cellular compartments. In the last reaction of the urea cycle, the cytosolic enzyme arginase cleaves arginine to yield urea and ornithine. Ornithine is transported into the mitochondria to initiate another round of the urea cycle.