Which of the following enzymes are involved with starch digestion?

December 20, 2025 •

2 min read

The human body relies on a precise series of digestive enzymes to break down complex carbohydrates like starch into simple, absorbable sugars. From the moment you begin chewing, specialized enzymes initiate and complete the intricate process of starch digestion, ensuring your body receives the necessary energy.

Quick Summary

This article details the specific enzymes responsible for breaking down dietary starch, starting in the mouth and continuing through the small intestine. It covers the roles of salivary and pancreatic amylase, as well as the brush border enzymes like maltase and alpha-dextrinase, in converting complex carbohydrates into absorbable glucose molecules.

Key Points

Salivary and Pancreatic Amylase: The main enzymes that initiate and continue the breakdown of starch into smaller sugar molecules, respectively.
Brush Border Enzymes: A group of enzymes located in the small intestine, including maltase and alpha-dextrinase, responsible for the final conversion of small saccharides into absorbable glucose.
Stomach Inactivation: The highly acidic environment of the stomach denatures and inactivates salivary amylase, stopping starch digestion temporarily.
Alpha-1,4 and Alpha-1,6 Bonds: Amylase breaks the alpha-1,4 bonds in starch, while alpha-dextrinase is needed to break the alpha-1,6 bonds at the branch points of amylopectin.
Maltose to Glucose: The disaccharide maltose, a primary product of amylase action, is further hydrolyzed into two glucose molecules by the enzyme maltase.
Optimal pH: Different enzymes involved in starch digestion have different optimal pH levels, with salivary amylase working best in a neutral environment and pancreatic amylase in a slightly alkaline one.

The Beginning of Starch Digestion: Salivary Amylase

Starch digestion starts in the mouth with salivary alpha-amylase (ptyalin), secreted by salivary glands. This enzyme breaks down starches into smaller carbohydrates like maltose. Chewing starchy foods longer can highlight this process as they may taste sweeter.

The Inactivation of Salivary Amylase in the Stomach

In the acidic stomach (pH 1.5-3.5), salivary amylase is inactivated, as enzymes are sensitive to extreme pH. The stomach primarily mixes food before it enters the small intestine.

The Primary Site of Starch Digestion: The Small Intestine

The small intestine is where most starch digestion occurs. Chyme from the stomach mixes with pancreatic and intestinal secretions in the duodenum.

Pancreatic Alpha-Amylase

The pancreas releases pancreatic alpha-amylase into the duodenum. This enzyme is potent and suited for the small intestine's alkaline environment. It breaks down remaining starch and smaller glucose chains into disaccharides (like maltose) and trisaccharides.

Brush Border Enzymes: The Final Stage

The final step of starch digestion happens on the small intestinal lining, specifically at the microvilli containing brush border enzymes (alpha-glucosidases). These enzymes convert small carbohydrate molecules into single glucose units for absorption. Key brush border enzymes include:

Maltase: Converts maltose into two glucose molecules.
Alpha-dextrinase (Isomaltase): Breaks down alpha-1,6 linkages in dextrins left from amylopectin digestion, which amylase cannot handle.
Sucrase: Aids in breaking down some small starch fragments in addition to its main role in sucrose digestion.

Comparison Table: Starch-Digesting Enzymes in Humans


Enzyme	Source	Location of Action	Substrate(s)	Primary Product(s)	Optimum pH
Salivary Alpha-Amylase (Ptyalin)	Salivary glands	Mouth	Starch (Amylose, Amylopectin)	Maltose, Maltotriose, Short Dextrins	~6.7
Pancreatic Alpha-Amylase	Pancreas	Small Intestine	Remaining Starch, Dextrins	Maltose, Maltotriose, Limit Dextrins	~7.0–8.0
Maltase	Small Intestinal Brush Border	Small Intestine	Maltose	Glucose	~6.0–7.0
Alpha-Dextrinase	Small Intestinal Brush Border	Small Intestine	Limit Dextrins	Glucose	~6.0–7.0

A Complete List of Enzymes Involved

Efficient starch breakdown requires several enzymes across the digestive system:

Salivary Amylase: Starts starch breakdown in the mouth.
Pancreatic Amylase: Handles the majority of starch breakdown in the small intestine.
Maltase: Breaks maltose into two glucose molecules.
Alpha-Dextrinase: Targets alpha-1,6 bonds in dextrins.
Sucrase: Can break down some small saccharides from starch digestion.

Conclusion

Amylase, in both salivary and pancreatic forms, is crucial for starch digestion. The process begins in the mouth, but the main work is done by pancreatic amylase in the small intestine. Brush border enzymes like maltase and alpha-dextrinase complete the breakdown, converting maltose and other oligosaccharides into absorbable glucose. This enzyme coordination ensures energy is obtained from complex carbohydrates. For more information on carbohydrate structures, refer to the Food and Agriculture Organization of the United Nations.

Frequently Asked Questions

The primary enzyme that breaks down starch is amylase. It is produced in the salivary glands and the pancreas and works by hydrolyzing the long polysaccharide chains of starch into smaller carbohydrate units.

Starch digestion begins in the mouth, where salivary glands release salivary alpha-amylase (ptyalin) to start breaking down complex starches into smaller sugars during chewing.

In the stomach, the acidic environment rapidly inactivates salivary amylase, halting the chemical breakdown of starch. The stomach's main role in this phase is mixing the food with gastric juices before it moves to the small intestine.

Pancreatic alpha-amylase is secreted into the small intestine to continue breaking down starch into maltose and other small saccharides. The final step is completed by brush border enzymes like maltase and alpha-dextrinase, which convert these into glucose.

Brush border enzymes, such as maltase and alpha-dextrinase, are attached to the microvilli of the small intestine. Their role is to break down the disaccharides and oligosaccharides created by amylase into absorbable monosaccharides like glucose.

No, starch cannot be effectively digested without amylase. Amylase is the key enzyme that cleaves the alpha-1,4 glycosidic bonds within starch molecules. Without it, starch would pass through the digestive system undigested, leading to digestive issues.

The final products of starch digestion are simple monosaccharides, primarily glucose, which are absorbed by the small intestine and used by the body for energy.