MALTASE-GLUCOAMYLASE: REGULATOR OF STARCH DIGESTION

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 1994年，在9名儿童中报告了一种新的葡糖淀粉酶缺乏和淀粉不耐受综合征。 该综合征的特征是慢性腹泻，这对从饮食中消除淀粉和淀粉低聚物有反应。 所有受试者的空肠葡萄糖淀粉酶活性水平均较低，组织学活检正常。1998年，我们报道了产生麦芽糖酶-葡糖淀粉酶（MGA）的基因的cDNA序列。 1999年，我们在本·陶布总医院发现了一例先天性MGA缺乏症。 由于活检葡萄糖水解酶的特异性活性和临床症状之间存在许多临床差异，并且由于MGA在远端小肠中的主要表达，因此有必要评估该患者体内淀粉的消化。 淀粉消化的平衡研究无效，因为结肠中存在淀粉消化的补救途径。已经开发了一种定量淀粉消化方案，其使用UL 13 C-淀粉/未标记的葡萄糖低聚物以恒定速率输注6小时，并测定血液中UL 13 C-葡萄糖的平台期外观。对原始方案的修改是用多糖恒定输注13 C-淀粉;使用UL-13 C-淀粉（99%APE）作为MGA底物;以及稳态定量血浆葡萄糖（M+6）同位素异构体作为输注淀粉产生的产物，以测量淀粉消化速率。 通过差异，剩余的输注的13 C-淀粉是呈现给结肠的用于补救消化的负荷。 在本申请中，我们希望测试空肠中的体外葡糖淀粉酶活性水平预测体内小肠淀粉消化的假设。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In 1994 a new syndrome of glucoamylase deficiency and starch intolerance was reported in nine children. The syndrome was characterized by chronic diarrhea which responded to elimination of starch and starch oligomers from the diet. The subjects all had low levels of jejunal glucoamylase activities and histologically normal biopsies. In 1998, we reported the sequence of the cDNA for the gene that produces maltase-glucoamylase (MGA). In 1999, we discovered a case of congenital MGA deficiency at the Ben Taub General Hospital. Because there are many clinical discrepancies between biopsy glucohydrolase specific activities and clinical symptoms and because of the predominant expression of MGA in distal small bowel, it was necessary to evaluate in vivo digestion of starch in this patient. Balance studies for starch digestion were not effective because of a salvage pathway for starch digestion existing in the colon. A quantitative starch digestion protocol has been developed that uses UL 13C-starch / unlabeled glucose oligomers infused at a constant rate for a period of 6 hours and determines plateau appearance of UL 13C-glucose in blood. Modifications over an original protocol were constant infusion of the 13C-starch with Polycose; and use of UL-13C-starch (99% APE) as MGA substrate; and steady state quantitation of plasma glucose (M+6) isotopomers as products arising from the infused starch to measure rate of starch digestion. By difference, the remaining infused 13C-starch is the load presented to the colon for salvage digestion. In this application we wish to test the hypothesis that level of in vitro glucoamylase activity in the jejunum predicts in vivo small intestinal starch digestion.