Digestion of dietary lipids – In the human small intestine, which enzyme is primarily responsible for hydrolyzing triacylglycerols from food?

Introduction / Context:
Efficient digestion and absorption of dietary fats require enzymatic hydrolysis of triacylglycerols to free fatty acids and monoacylglycerols. The key catalyst in the lumen of the small intestine is pancreatic lipase, assisted by colipase and bile salts. This question assesses recognition of the principal enzyme and location.

Given Data / Assumptions:

• Bile acids emulsify fats, increasing surface area for enzymes.
• Pancreatic lipase is secreted into the duodenum and jejunum.
• Hydrolysis products form mixed micelles for uptake by enterocytes.

Concept / Approach:
Pancreatic triacylglycerol lipase cleaves ester bonds at the sn-1 and sn-3 positions, yielding two free fatty acids and 2-monoacylglycerol. Colipase anchors lipase to the lipid–water interface in the presence of bile salts, ensuring high activity in the intestinal milieu. Other listed enzymes are not lipases and do not hydrolyze dietary triacylglycerols.

Step-by-Step Solution:

Verification / Alternative check:
Pancreatic insufficiency reduces fat absorption and causes steatorrhea; enzyme replacement therapy with lipase improves digestion, confirming its pivotal role.

Why Other Options Are Wrong:

• Adenylate cyclase and protein kinase A are signaling enzymes.
• Amylase digests starch; pepsin digests proteins in the stomach.

Common Pitfalls:
Confusing “gastric lipase” (minor contributor) with the major intestinal enzyme “pancreatic lipase.”

Final Answer:
Triacylglycerol lipase secreted by the pancreas (pancreatic lipase)