Disaccharidase activities in dyspeptic children: Biochemical and molecular investigations of maltase-glucoamylase activity

Background: Maltase-glucoamylase enzyme plays an important role in starch digestion. Glucoamylase deficiency is reported to cause chronic diarrhea in infants, but its role in dyspeptic children is unknown. Methods: Glucoamylase and other disaccharidase specific activities were assayed from duodenal biopsy specimens in 44 children aged 0.5-18 years (mean, 10 ± 5 years) undergoing endoscopy to evaluate dyspeptic symptoms. All subjects had normal duodenal histology. Intestinal organ culture was used to evaluate synthesis and processing of maltase-glucoamylase. Sequencing of the maltase-glucoamylase coding region was performed in subjects with low activity or variation of isoform in organ culture. Results: Twenty-two of the dyspeptic children had one or more disaccharidases with low specific activity. Twelve subjects (28%) had low activity of glucoamylase. Eight subjects had low activities of glucoamylase, sucrase, and lactase. Low glucoamylase activity was not correlated with the isoform phenotype of maltase-glucoamylase as described by metabolic labeling and sodium dodecyl sulfate electrophoresis. Novel nucleotide changes were not detected in one subject with low glucoamylase activity or in two subjects with variant isoforms maltase-glucoamylase peptides. Conclusion: Twelve of 44 dyspeptic children had low specific activity of duodenal maltase-glucoamylase. Eight of these children had low specific activity of all measured disaccharidases.