Biosynthesis of sucrase-isomaltase in the small intestine hereditarily deficient in sucrase activity

对蔗糖的不耐受是由于缺乏与小肠刷状缘膜相关的蔗糖酶-异麦芽糖酶所致。我们在家麝鼠的一些品系中发现了遗传性蔗糖酶缺乏症。首先，我们从正常个体和突变个体中分别纯化了正常蔗糖酶异麦芽糖酶和异常无蔗糖酶异麦芽糖酶，并对其性质进行了研究。蔗糖酶和异麦芽糖酶分别为116 kDa和96 kDa。麦芽糖酶的活性主要归因于蔗糖。其次，我们在兔体内制备了针对纯化的正常复合体的抗体。试管定量沉淀结果表明，正常蔗糖酶异麦芽糖酶和无蔗糖酶异麦芽糖酶位于同一微绒毛中，即它们被合成并运输到同一细胞的刷状缘膜上。与膜相关的酶，无论是正常的还是突变的，都与抗体发生部分反应，对目前的免疫形态学方法构成了严重的问题。

Intolerance to sucrose is caused by lack of sucrase-isomaltase associated with the brush border membrane of the small intestine. We have found hereditary sucrase deficiency in some strains of the house musk shrew, Suncus murinus. In the present work we aimed at immunochemically elucidating the intracellular pathway of biosynthesis of (sucrase-) isomaltase in the Suncus intestine hereditarity deficient in sucrase activity.First, we have purified normal sucrase-isomaltase and abnormal sucrase-free isomaltase from normal and mutant indibiduals, respectively, and investigated their properties. Sucrase and isomaltase was of 116 and 96 kDa, respectively. The maltase activity of the complex was mainly ascribed to sucrase.Second, we prepared antibodies against the purified normal complex in a rabbit. The results of quantitative precipitation in test tube showed that normal sucrase-isomaltase and sucrase-free isomaltase were located in the same microvillus ; that is, they were synthesized and transported to the brush border membrane in the same cell. The enzymes associated with the membrane, normal or mutant, partially reacted with the antibodies, posing a serious problem to immunomorphological approaches such as the present one.