Which is not a zymogen

Options

A. Trypsinogen
B. Pepsinogen
C. Angiotensin II
D. Procollagenase

Answer

To determine which option is not a zymogen, we need to understand what a zymogen is. A zymogen is an inactive precursor of an enzyme that requires a biochemical change to become an active enzyme. Here’s a step-by-step solution to the question:

### Step-by-Step Solution:

1. **Define Zymogen**: Zymogens are inactive enzyme precursors that are activated in the digestive system. They are secreted by various glands and must undergo a transformation to become active enzymes.

2. **Analyze the Options**:
- **Option 1: Trypsinogen**: This is a zymogen secreted by the pancreas. It is activated to trypsin in the small intestine. Therefore, this is a zymogen.
- **Option 2: Pepsinogen**: This is another zymogen, secreted by the gastric glands in the stomach. It is activated by hydrochloric acid (HCl) to form pepsin. Thus, this is also a zymogen.
- **Option 3: Angiotensin II**: This is the active form of angiotensinogen, which is produced by the liver. Angiotensin II is involved in regulating blood pressure and is not an inactive precursor. Therefore, this is not a zymogen.
- **Option 4: Procollagenase**: This is a zymogen that is activated to collagenase, which is involved in the breakdown of collagen. Hence, this is also a zymogen.

3. **Conclusion**: Among the options provided, angiotensin II is the only one that is not a zymogen. Therefore, the correct answer is **Option 3: Angiotensin II**.