SucraseSucrase-Isomaltase Complex: An enzyme complex found in the brush border membranes of the small intestine. It is believed to be an enzyme complex with different catalytic sites. Its absence is manifested by an inherited disease called sucrase-isomaltase deficiency.DisaccharidasesOligo-1,6-Glucosidase: An enzyme that catalyzes the endohydrolysis of 1,6-alpha-glucosidic linkages in isomaltose and dextrins produced from starch and glycogen by ALPHA-AMYLASES. EC 18.104.22.168.alpha-Glucosidases: Enzymes that catalyze the exohydrolysis of 1,4-alpha-glucosidic linkages with release of alpha-glucose. Deficiency of alpha-1,4-glucosidase may cause GLYCOGEN STORAGE DISEASE TYPE II.Jejunum: The middle portion of the SMALL INTESTINE, between DUODENUM and ILEUM. It represents about 2/5 of the remaining portion of the small intestine below duodenum.Intestine, Small: The portion of the GASTROINTESTINAL TRACT between the PYLORUS of the STOMACH and the ILEOCECAL VALVE of the LARGE INTESTINE. It is divisible into three portions: the DUODENUM, the JEJUNUM, and the ILEUM.Microvilli: Minute projections of cell membranes which greatly increase the surface area of the cell.Sucrose: A nonreducing disaccharide composed of GLUCOSE and FRUCTOSE linked via their anomeric carbons. It is obtained commercially from SUGARCANE, sugar beet (BETA VULGARIS), and other plants and used extensively as a food and a sweetener.Lactase: An enzyme which catalyzes the hydrolysis of LACTOSE to D-GALACTOSE and D-GLUCOSE. Defects in the enzyme cause LACTOSE INTOLERANCE.Glucosidases: Enzymes that hydrolyze O-glucosyl-compounds. (Enzyme Nomenclature, 1992) EC 3.2.1.-.Intestinal Mucosa: Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI.Carbohydrate Metabolism, Inborn ErrorsLactase-Phlorizin Hydrolase: The multifunctional protein that contains two enzyme domains. The first domain (EC 22.214.171.124) hydrolyzes glycosyl-N-acylsphingosine to a sugar and N-acylsphingosine. The second domain (EC 126.96.36.199) hydrolyzes LACTOSE and is found in the intestinal brush border membrane. Loss of activity for this enzyme in humans results in LACTOSE INTOLERANCE.Leucyl Aminopeptidase: A zinc containing enzyme of the hydrolase class that catalyzes the removal of the N-terminal amino acid from most L-peptides, particularly those with N-terminal leucine residues but not those with N-terminal lysine or arginine residues. This occurs in tissue cell cytosol, with high activity in the duodenum, liver, and kidney. The activity of this enzyme is commonly assayed using a leucine arylamide chromogenic substrate such as leucyl beta-naphthylamide.Intestines: The section of the alimentary canal from the STOMACH to the ANAL CANAL. It includes the LARGE INTESTINE and SMALL INTESTINE.Glycoside Hydrolasesbeta-Fructofuranosidase: A glycoside hydrolase found primarily in PLANTS and YEASTS. It has specificity for beta-D-fructofuranosides such as SUCROSE.Mucositis: An INFLAMMATION of the MUCOSA with burning or tingling sensation. It is characterized by atrophy of the squamous EPITHELIUM, vascular damage, inflammatory infiltration, and ulceration. It usually occurs at the mucous lining of the MOUTH, the GASTROINTESTINAL TRACT or the airway due to chemical irritations, CHEMOTHERAPY, or radiation therapy (RADIOTHERAPY).Indolizinesbeta-Galactosidase: A group of enzymes that catalyzes the hydrolysis of terminal, non-reducing beta-D-galactose residues in beta-galactosides. Deficiency of beta-Galactosidase A1 may cause GANGLIOSIDOSIS, GM1.Jejunoileal Bypass: A procedure consisting of the SURGICAL ANASTOMOSIS of the proximal part of the JEJUNUM to the distal portion of the ILEUM, so as to bypass the nutrient-absorptive segment of the SMALL INTESTINE. Due to the severe malnutrition and life-threatening metabolic complications, this method is no longer used to treat MORBID OBESITY.Galactosidases: A family of galactoside hydrolases that hydrolyze compounds with an O-galactosyl linkage. EC 3.2.1.-.Maltose: A dextrodisaccharide from malt and starch. It is used as a sweetening agent and fermentable intermediate in brewing. (Grant & Hackh's Chemical Dictionary, 5th ed)Ileum: The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.Isomaltose: A disaccharide consisting of two glucose units in an alpha (1-6) glycosidic linkage.Antigens, CD13: Zinc-binding metalloproteases that are members of the type II integral membrane metalloproteases. They are expressed by GRANULOCYTES; MONOCYTES; and their precursors as well as by various non-hematopoietic cells. They release an N-terminal amino acid from a peptide, amide or arylamide.