Sucrase isomaltase deficiency is a disorder that affects the normal digestion of carbohydrates and therefore their absorption, and leads to sucrose intolerance. Intolerance is described as clinical symptoms caused by sugar malabsorption (Scriver et al, 2001). In the case of sucrose intolerance, it refers to the inability to digest and absorb sucrose, leading to several abdominal symptoms. Although sucrase isomaltase deficiency is not a life-threatening condition, it can cause discomfort and therefore dietary changes should be made in order to avoid the symptoms caused by the deficiency. Carbohydrates account for about half of the energy humans get from food. Digestion and absorption of carbohydrates pass through the brush border limb which has an apical and basolateral membrane. Anchored to the brush border membrane are enzymes involved in the digestion of disaccharides (Silverthorn, 2010). Carbohydrates can only be absorbed as monosaccharides, which means that polysaccharide and disaccharide carbohydrates must first be hydrolyzed into monosaccharides. Carbohydrate digestion begins in saliva and the stomach where alpha-amylase hydrolyzes the alpha-1,4 glycosidic bonds between glucose molecules in starch, forming maltotriose, the disaccharide. maltose and dextrin are made up of five to ten glucose molecules (Lim, 2007). The disaccharides sucrose and lactose come directly from food. There are four enzymes present on the brush border membrane, responsible for the hydrolysis of sucrose, lactose and starch breakdown products into monosaccharides so that they can be absorbed (Lieberman et al, 2007) . These enzymes are known as glycosidases and include: glucoamylase, lactase, trehalase and sucrase isomaltase (Lieberman et al, 2007). Sucrase isomaltase...... middle of paper...... Biol Chem, Volume 281. Lieberman M, Marks A, Smith C. (2007). The essential principles of medical biochemistry are a clinical approach. Philadelphia: Lippincott Williams & Wilkins. Pp 316-317. Ouwendijk J, Moolenaar C, Peters WJ, Hollenberg CP, Ginsel LA, Fransen J et al. (1996). Congenital sucrase-isomaltase deficiency identification of a glutamine to proline substitution that leads to a block in sucrase-isomaltase transport in the pre-Golgi compartment. J Clin Invest, Volume 97. Lim M, Roach J. (2007). Metabolism and nutrition. 3rd ed. Edinburgh: Mosby. Pp 145Scriver, Charles R, Beaudet, Arthur L, Sly, William S, et al. (2001). The metabolic and molecular bases of hereditary diseases. 8th ed. London: McGraw-Hill. Pp 1634-1639.Silverthorn DU. (2010). Human physiology: an integrated approach. 5th ed. San Francisco, California; London: Pearson/Benjamin Cummings. PP 703-704.