What is the role of brush border enzymes in the small intestine?

• A. They begin the digestion of proteins in the stomach.
• B. They absorb bile acids.
• C. They perform the final digestion of disaccharides and peptides to monosaccharides and amino acids.
• D. They secrete hormones into the bloodstream.

Answer: (C)

Brush border enzymes on the microvilli of small-intestinal absorptive cells finish the job of digestion by breaking down disaccharides into monosaccharides and cleaving small peptides into amino acids and tiny peptides. This final step is what makes the nutrients ready for absorption into the enterocytes. Pancreatic enzymes have already started the work in the intestinal lumen, but the last cuts occur right at the brush border so the resulting monosaccharides and amino acids can be efficiently taken up. The other options don’t fit because stomach digestion is driven by pepsin, not brush border enzymes; bile acids are absorbed by dedicated transport processes in the ileum rather than by these enzymes; and hormone secretion comes from enteroendocrine cells, not from brush border enzymes.