Question

Which enzyme is primarily responsible for the breakdown of proteins in the intestine of fishes?

• A. Amylase
• B. Lipase
• C. Pepsin
• D. Trypsin

Hint:

Remember that pepsin is stomach-associated (acidic), whereas trypsin is intestine-associated (alkaline) in stomach-bearing fishes.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Proteolytic enzymes, also known as proteases, are biological catalysts responsible for hydrolyzing peptide bonds within proteins.
In fishes, different regions of the digestive tract operate at distinct pH levels, requiring specific enzymes to function optimally.

Step 2: Detailed Explanation:
Pepsin is an acidic protease that is highly active in the stomach of gastric fishes, operating at a very low pH.
Once chyme passes from the stomach into the intestine, pancreatic secretions neutralize the acid, raising the pH to neutral or alkaline levels.
Trypsin, an alkaline serine protease secreted by the pancreas (or hepatopancreas in some fishes), becomes highly active in this alkaline intestinal environment.
It cleaves peptide bonds specifically at the carboxyl side of lysine and arginine residues, playing the lead role in intestinal protein digestion.
Amylase is responsible for digesting carbohydrates, and lipase is responsible for digesting lipids, leaving trypsin as the primary intestinal protease.

Step 3: Final Answer:
Therefore, trypsin is the primary enzyme responsible for protein breakdown in the alkaline environment of the fish intestine.