Which one of the following enzymes is secreted both by exocrine pancreas and by intestinal mucosa?
## **Core Concept**
The question tests knowledge of pancreatic and intestinal enzymes, specifically focusing on their sites of secretion. The exocrine pancreas secretes various digestive enzymes into the duodenum, while the intestinal mucosa secretes enzymes involved in final carbohydrate and protein digestion.
## **Why the Correct Answer is Right**
The correct answer, , is an enzyme that catalyzes the hydrolysis of disaccharides into simple sugars. It is secreted by the exocrine pancreas as well as by the intestinal mucosa, specifically by the brush border membrane of enterocytes. This dual secretion allows for both pancreatic and intestinal digestion of carbohydrates.
## **Why Each Wrong Option is Incorrect**
- **Option A:** is primarily involved in the digestion of fats and is secreted by the exocrine pancreas. While crucial for lipid digestion, it does not match the criteria of being secreted by both the pancreas and intestinal mucosa.
- **Option B:** is a pancreatic enzyme that breaks down proteins into smaller peptides. It is secreted by the exocrine pancreas but not significantly by the intestinal mucosa.
- **Option D:** is involved in carbohydrate digestion and is secreted by the salivary glands and pancreas but not by the intestinal mucosa.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while the pancreas secretes a wide array of digestive enzymes, the intestinal mucosa itself secretes enzymes critical for the final steps of digestion, such as and . This highlights the importance of both pancreatic and intestinal contributions to nutrient digestion and absorption.
## **Correct Answer:** .