ACS Biochemistry Practice Exam

The enzyme responsible for converting arginine to ornithine in the urea cycle is arginase. This reaction is significant because it is the final step of the urea cycle, which occurs in the liver and is critical for the detoxification of ammonia, a byproduct of amino acid metabolism.

Arginase catalyzes the hydrolysis of arginine to ornithine and urea, facilitating the elimination of excess nitrogen from the body. The ornithine produced enters the urea cycle again, contributing to the ongoing process of nitrogen detoxification. This interaction helps maintain nitrogen balance in the body.

This specific activity of arginase highlights its role as an essential enzyme in the metabolic pathway that prevents ammonia accumulation, which can be toxic at high levels. Therefore, recognizing arginase's function is pivotal for understanding the urea cycle's importance in amino acid catabolism and overall nitrogen metabolism.