Sucrase is an enzyme, playing a specific role in the digestion of sugars. Enzymes are biological catalysts, specialized proteins that accelerate chemical reactions within living organisms without being consumed. Sucrase specifically targets sucrose, commonly known as table sugar, to break it down into simpler forms the body can use.
What Sucrase Is
Sucrase is an enzyme important for carbohydrate digestion. It is produced and functions in the small intestine, specifically on the brush border of the enterocytes, the absorptive cells lining the intestine. The brush border is a specialized surface composed of numerous microvilli that increase the area for nutrient absorption.
Sucrase-isomaltase, the human form of the enzyme, is an integral membrane protein anchored in this brush border. Its structure includes two catalytic subunits, sucrase and isomaltase, formed from a single precursor protein. The enzyme exhibits high specificity, primarily acting on sucrose.
How Sucrase Works in Digestion
Sucrase facilitates the breakdown of sucrose, a disaccharide, into its monosaccharides: glucose and fructose. Sucrose is composed of these two simpler sugars linked by a glycosidic bond. When sucrose enters the small intestine, sucrase binds to it at a specific region called the active site, much like a key fits into a lock. This binding stresses the glycosidic bond within the sucrose molecule.
The enzyme then catalyzes a hydrolysis reaction, adding a water molecule to break this bond. This process releases glucose and fructose molecules. Once broken down, these smaller sugar molecules are absorbed through the intestinal wall into the bloodstream. From the bloodstream, glucose and fructose are transported to cells throughout the body, where they are used for energy production and metabolic functions.
When Sucrase Doesn’t Work Properly
When sucrase does not function correctly, sucrose cannot be broken down and absorbed in the small intestine. This undigested sucrose then passes into the large intestine. There, gut bacteria ferment the undigested sugar. This fermentation produces gases and other byproducts, leading to uncomfortable gastrointestinal symptoms.
Common symptoms of sucrose intolerance include bloating, excess gas, stomach cramps, and diarrhea. Sucrase deficiency can be genetic, known as congenital sucrase-isomaltase deficiency (CSID), or acquired due to intestinal lining damage. Diagnosis involves assessing symptoms and can be confirmed through tests like a sucrose breath test. Management involves dietary adjustments to limit sucrose intake.