Which enzymes are produced by the intestinal brush border for carbohydrate digestion?

• A. Maltase, sucrase, lactase, and isomaltase
• B. Lipase, protease, amylase
• C. Peptidase, nuclease, sucrase
• D. Lactase only

Answer: (A)

Carbohydrate digestion in the small intestine is completed by enzymes located on the microvilli of enterocytes, the brush border. These enzymes cleave disaccharides into monosaccharides so they can be absorbed. The enzymes specific to this final step are maltase, sucrase, lactase, and isomaltase. Maltase acts on maltose (and related dextrins) to yield glucose; sucrase splits sucrose into glucose and fructose; lactase breaks lactose into glucose and galactose; isomaltase works on isomaltose and limit dextrins. These are membrane-bound enzymes produced by intestinal cells, distinct from pancreatic enzymes that operate in the lumen.

Other options mix in enzymes that digestion relies on elsewhere (like lipase or proteases) or omit important brush border activities. For carbohydrate digestion at the brush border, the four enzymes listed here are the correct set.