Nichols Buford L, Baker Susan S, Quezada-Calvillo Roberto
Department of Pediatrics and Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX.
Digestive Diseases and Nutrition Center, Jacobs School of Medicine and Biomedical Sciences, Buffalo, NY.
J Pediatr Gastroenterol Nutr. 2018 Jun;66 Suppl 3:S24-S29. doi: 10.1097/MPG.0000000000001955.
The mucosal maltase enzymes are characterized by an activity that produces glucose from linear glucose polymers, assayed with the disaccharide maltose. The related enzyme isomaltase produces glucose from branched glucose polymers, assayed with palatinose. Maltase and isomaltase activities are part of the 4 disaccharidases assayed from clinical duodenal biopsy homogenates. The reported maltase activities are more difficult to interpret than lactase or sucrase activities because both the sucrase-isomaltase and maltase-glucoamylase proteins have overlapping maltase activities. The early work of Dahlqvist identified 4 maltase activities from human small intestinal mucosa. On one peptide, sucrase (maltase Ib) and isomaltase (maltase Ia) activities shared maltase activities but identified the enzymes as sucrase-isomaltase. On the other peptide, no distinguishing characteristics of the 2 maltase activities (maltases II and III) were detected and the activities identified as maltase-glucoamylase. The nutritional/clinical importance of small intestinal maltase and isomaltase activities are due to their crucial role in the digestion of food starches to absorbable free glucose. This review focuses on the interpretation of biopsy maltase activities in the context of reported lactase, sucrase, maltase, and palatinase biopsy assay activity patterns. We present a classification of mucosal maltase deficiencies and novel primary maltase deficiency (Ib, II, III) and provide a clarification of the role of maltase activity assayed from clinically obtained duodenal biopsies, as a path toward future clinical and molecular genomic investigations.
黏膜麦芽糖酶的特点是具有一种活性，即能从线性葡萄糖聚合物中产生葡萄糖，通过二糖麦芽糖进行测定。相关的异麦芽糖酶能从分支葡萄糖聚合物中产生葡萄糖，通过帕拉金糖进行测定。麦芽糖酶和异麦芽糖酶的活性是临床十二指肠活检匀浆中检测的4种双糖酶活性的一部分。所报道的麦芽糖酶活性比乳糖酶或蔗糖酶活性更难解释，因为蔗糖酶-异麦芽糖酶和麦芽糖酶-葡糖淀粉酶蛋白都具有重叠的麦芽糖酶活性。达尔奎斯特的早期研究从人小肠黏膜中鉴定出4种麦芽糖酶活性。在一种肽上，蔗糖酶（麦芽糖酶Ib）和异麦芽糖酶（麦芽糖酶Ia）的活性具有共同的麦芽糖酶活性，但将这些酶鉴定为蔗糖酶-异麦芽糖酶。在另一种肽上，未检测到这两种麦芽糖酶活性（麦芽糖酶II和III）的区别特征，这些活性被鉴定为麦芽糖酶-葡糖淀粉酶。小肠麦芽糖酶和异麦芽糖酶活性在营养/临床上的重要性在于它们在将食物淀粉消化为可吸收的游离葡萄糖方面的关键作用。本综述重点关注在报道的乳糖酶、蔗糖酶、麦芽糖酶和帕拉廷酶活检测定活性模式的背景下对活检麦芽糖酶活性的解释。我们提出了黏膜麦芽糖酶缺乏症和新型原发性麦芽糖酶缺乏症（Ib、II、III）的分类，并对从临床获取的十二指肠活检中检测到的麦芽糖酶活性的作用进行了澄清，作为未来临床和分子基因组研究的一条途径。
