SI（sucrase-isomaltase），癌症关联基因，基因ID：6476，该基因编码一种在肠道刷缘表达的蔗糖酶-异麦芽糖酶编码蛋白被合成为前体蛋白，被胰腺蛋白酶切割成蔗糖酶和异麦芽糖酶两个酶亚单位。这两个亚基异源二聚形成蔗糖异麦芽糖酶复合物。这种复合物对于消化包括淀粉、蔗糖和异麦芽糖在内的膳食碳水化合物是必不可少的。该基因突变是先天性蔗糖酶-异麦芽糖酶缺乏症的原因。[由RefSeq提供，2010年4月]This gene encodes a sucrase-isomaltase enzyme that is expressed in the intestinal brush border. The encoded protein is synthesized as a precursor protein that is cleaved by pancreatic proteases into two enzymatic subunits sucrase and isomaltase. These two subunits heterodimerize to form the sucrose-isomaltase complex. This complex is essential for the digestion of dietary carbohydrates including starch， sucrose and isomaltose. Mutations in this gene are the cause of congenital sucrase-isomaltase deficiency.[provided by RefSeq， Apr 2010]。