Sucrase breaks down sucrose to glucose and fructose. It’s secreted by the tips of the villi of the epithelium of the small intestine.
When sucrase isn’t secreted in the small intestine it’s called sucrose intolerance, or Congenital Sucrase-Isomaltase Deficiency. The result is excess gas production with diarrhea and malabsorption. Sucrase-Isomaltase Deficiency is a rare autosomal recessive disorder where there is complete absence of sucrase and most of the maltase digestive activity. It usually presents itself at weaning from breast milk when the infants are first exposed to the offending carbohydrates. When disaccharides and oligosaccharides are ingested, there is a failure to breakdown sucrose into fructose and glucose and the result in an osmotic-fermentative diarrhea. Occasionally patients won’t complain until late childhood or adulthood but a careful history usually indicates that symptoms have appeared earlier. The mainstay of treatment is dietary restriction of foods, which contain sucrose.
Sucrase production is also reduced in celiac sprue. Its levels increase in pregnancy, lactation and diabetes.