saccharase

Saccharase, commonly known as sucrase, is a digestive enzyme that catalyzes the hydrolysis of sucrose into its monosaccharide components, glucose and fructose. In humans and other mammals, saccharase activity is produced by enterocytes in the small intestine as part of the brush-border enzyme complex sucrase–isomaltase, where it acts on dietary sucrose during digestion. In plants and yeast, a related enzyme called invertase performs similar hydrolysis of sucrose and plays a key role in sugar metabolism and transport.

The enzyme cleaves the glycosidic bond linking glucose and fructose in sucrose by adding a water molecule, yielding equimolar glucose and fructose. It generally operates without the need for cofactors, with an optimal pH around the mildly acidic to near-neutral range, consistent with the conditions of the small intestine. The reaction proceeds with high specificity for the α-D-glucopyranosyl–(1→2)–β-D-fructofuranoside linkage in sucrose.

Genetics and clinical relevance: In humans, the sucrase–isomaltase (SI) gene encodes the enzyme activity. Defects in SI can cause congenital sucrase–isomaltase deficiency (CSID), leading to malabsorption, chronic diarrhea, bloating, and gas after consumption of sucrose and starch. Diagnosis may involve enzymatic assays or genetic testing, and management typically includes dietary modification to limit sucrose and starch, with enzyme replacement therapy used in some cases.

Industrial and nutritional roles: Invertase and related saccharases are produced commercially from microbial sources to generate invert sugar, a mixture of glucose and fructose. Invert sugar is used in confectionery, baking, beverages, and fermentation for its sweeter profile, improved texture, and reduced crystallization compared with sucrose.