One of the following is not an enzyme of digestive system

Options

A. Enterokinase
B. Amylase
C. Trypsin
D. Enterogasterone

Answer

To determine which of the following is not an enzyme of the digestive system, we will analyze each option given:

1. **Enterokinase**:
- Enterokinase is a proteolytic enzyme that acts on trypsinogen, converting it into trypsin. Since it is involved in the digestion of proteins, it is indeed an enzyme of the digestive system.

2. **Amylase**:
- Amylase is another digestive enzyme that helps in the breakdown of carbohydrates. It is produced in the saliva and pancreas, making it a crucial enzyme in the digestive process. Therefore, amylase is also an enzyme of the digestive system.

3. **Trypsin**:
- Trypsin is an enzyme that acts on proteins, breaking them down into smaller peptides and amino acids. It is activated from trypsinogen by enterokinase and is a key enzyme in protein digestion. Thus, trypsin is also an enzyme of the digestive system.

4. **Enterogastron**:
- Enterogastron is a hormone secreted by the duodenal mucosa. It is not an enzyme; instead, it regulates digestive processes by inhibiting gastric movement and secretion. Therefore, enterogastron is not an enzyme of the digestive system.

Based on this analysis, the answer to the question is **Enterogastron**, as it is the only option that is not an enzyme.

### Summary of the Solution:
- Enterokinase: Enzyme (activates trypsin)
- Amylase: Enzyme (breaks down carbohydrates)
- Trypsin: Enzyme (digests proteins)
- Enterogastron: Not an enzyme (hormone that regulates digestion)

**Final Answer**: Enterogastron is not an enzyme of the digestive system.