Abnormal circulating enzyme concentration or activity Decreased mucosal sucrase-isomaltase activity 2021-01-30T13:48:50Z Sucrase-isomaltase has two subunits, sucrase and isomaltase. Isomaltase cleaves branched (1-6 linked) alpha-limit dextrins, while sucrase digests sucrose, maltose, short 1-4 linked glucose oligomers, and some branched starches into sugar monomers for intestinal absorption. Deficiency of this enzyme can lead to osmotic diarrhea, mild steatorrhea, chronic diarrhea, irritability, and vomiting after consuming sucrose. Reduced activity of the linked disaccharidase, sucrase-isomaltase, which is a glycoprotein localized to the brush border membrane of small intestinal villi.