Main function of enterokinase is:

Options

A. conversion of casein into paracasein
B. conversion of pepsinogen into pepsin
C. conversion of trypsinogen into trypsin
D. conversion of trypsin into trypsinogen

Explanation

To solve the question regarding the main function of enterokinase, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Enterokinase**:
- Enterokinase, also known as enteropeptidase, is an enzyme produced by the cells of the duodenum (the first part of the small intestine). Its primary role is to facilitate digestion.

**Hint**: Remember that enterokinase is linked to the activation of other digestive enzymes.

2. **Identify the Substrates**:
- The question provides several options regarding what enterokinase acts upon:
- Casein to paracasein
- Pepsinogen to pepsin
- Trypsinogen to trypsin
- Trypsin to trypsinogen

**Hint**: Focus on the specific enzymes mentioned and their inactive and active forms.

3. **Evaluate Each Option**:
- **Option 1**: Conversion of casein into paracasein is done by the enzyme renin, not enterokinase.
- **Option 2**: Conversion of pepsinogen into pepsin is catalyzed by hydrochloric acid (HCl), not enterokinase.
- **Option 3**: Conversion of trypsinogen into trypsin is the primary function of enterokinase. Trypsin is the active form that further activates other digestive enzymes.
- **Option 4**: Conversion of trypsin into trypsinogen is incorrect as trypsin is already the active form.

**Hint**: Eliminate options that do not involve enterokinase directly.

4. **Select the Correct Answer**:
- Based on the evaluations, the correct answer is **Option 3: conversion of trypsinogen into trypsin**. This is the main function of enterokinase, leading to the activation of other pancreatic enzymes.

**Hint**: Recall that the activation of trypsinogen is crucial for the digestion process.

### Final Answer:
The main function of enterokinase is the conversion of trypsinogen into trypsin (Option 3).