Which one of the following is not a zymogen ?

Options

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

Answer

To determine which of the following is not a zymogen, we need to analyze each option given in the question:

1. **Trypsinogen**: This is an inactive precursor of the enzyme trypsin. It is produced in the pancreas and is activated in the small intestine. Therefore, trypsinogen is a zymogen.

2. **Pepsinogen**: Similar to trypsinogen, pepsinogen is an inactive precursor of the enzyme pepsin. It is secreted by the stomach and activated in the acidic environment of the stomach. Thus, pepsinogen is also a zymogen.

3. **Procollagenase**: This is another inactive precursor, specifically of collagenase. It is involved in the breakdown of collagen and is activated to collagenase. Hence, procollagenase is a zymogen as well.

4. **Angiotensin**: Unlike the previous options, angiotensin is not an enzyme or an inactive precursor of an enzyme. Instead, it is a peptide hormone that acts as a powerful vasoconstrictor, increasing blood pressure and influencing kidney function. Therefore, angiotensin is not a zymogen.

Based on this analysis, the answer to the question "Which one of the following is not a zymogen?" is **angiotensin**.

### Summary of Steps:
1. Identify each option as a zymogen or not.
2. Analyze trypsinogen - confirmed as a zymogen.
3. Analyze pepsinogen - confirmed as a zymogen.
4. Analyze procollagenase - confirmed as a zymogen.
5. Analyze angiotensin - confirmed as not a zymogen.
6. Conclude that the correct answer is angiotensin.