`NH_(3)` change into urea in presence of

Options

A. Arginase enzyme
B. Urease enzyme
C. Xanthine oxidase
D. Uricase

Answer

To solve the question "NH₃ changes into urea in the presence of," we need to analyze the urea cycle and identify the correct enzyme involved in the conversion of ammonia (NH₃) to urea.

### Step-by-Step Solution:

1. **Understanding the Urea Cycle**: The urea cycle is a series of biochemical reactions that occur primarily in the liver. Its main purpose is to convert ammonia, which is toxic at high levels, into urea, which can be safely excreted from the body.

2. **Identifying the Starting Substrates**: The urea cycle begins with ammonia (NH₃) and carbon dioxide (CO₂). These substrates are essential for the synthesis of urea.

3. **First Step of the Urea Cycle**: The first reaction in the urea cycle is the formation of carbamoyl phosphate from ammonia and carbon dioxide. This reaction is catalyzed by the enzyme **carbamoyl phosphate synthetase**.

4. **Formation of Citrulline**: Carbamoyl phosphate then combines with ornithine to form citrulline, facilitated by the enzyme **ornithine transcarbamylase**.

5. **Conversion to Argininosuccinate**: Citrulline is converted to argininosuccinate with the help of the enzyme **argininosuccinate synthetase**.

6. **Hydrolysis of Argininosuccinate**: Argininosuccinate undergoes hydrolysis to produce arginine and fumarate. This reaction is catalyzed by the enzyme **argininosuccinate lyase**.

7. **Final Step - Formation of Urea**: The last step involves the conversion of arginine back to ornithine, which releases urea. This reaction is catalyzed by the enzyme **arginase**. This is the key step where urea is formed from arginine, and ammonia is released.

8. **Conclusion**: Among the options provided, the enzyme responsible for the conversion of ammonia to urea is **arginase**. Therefore, the correct answer is **arginase enzyme**.

### Final Answer:
**Arginase enzyme**

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