Background: Starch digestion is dependent on a combination of pancreatic and salivary amylase and the intestinal brush border enzymes glucoamylase and sucrase-isomaltase. Glucoamylase splits successive glucose molecules from the nonreducing end of starch molecules and is particularly important in infants who are relatively deficient in pancreatic amylase.
Methods: The authors measured glucoamylase activity in endoscopic mucosal biopsies submitted for measurement of disaccharidase activity from 214 patients aged 1 month to 20 years. Glucoamylase activity was measured using glucose polymers (polycose) as the substrate. The authors also related enzyme activity to histologic appearance and clinical indication for endoscopy.
Results: The most common reasons for biopsy were abdominal pain, gastroesophageal reflux, and vomiting. Disaccharidase activity by age was similar to previous reports. Glucoamylase activity did not differ with age, but was 2 to 3 times the activity reported previously. Glucoamylase activity was significantly depressed in children with the most severe histologic abnormalities. Normal glucoamylase activity (+/-2 SD) was 80.6 +/- 54.8 micromoles of glucose produced per minute per gram of protein.
Conclusions: Glucoamylase activity is 2 to 3 times higher when glucose polymers are used as substrate than when glycogen is used. Severe mucosal disease is associated with reduced glucoamylase activity. Quantitation of glucoamylase activity with glucose polymers is more appropriate in evaluating children since these polymers are commonly used as carbohydrate source in the diet.