Fructose-1-phosphate and fructose-1,6-bisphosphate aldolases in the small intestinal mucosa.

Reference values are presented for the activity of fructose-1-phosphate aldolase (F1PA) and fructose-1,6-bisphosphate aldolase (FBPA) in the small intestinal mucosa of 32 nonaffected children, 8 nonaffected adults and 2 children with hereditary fructose intolerance (HFI). The 96% confidence limits for F1PA in children are 1.55 to 43.0 u/g protein, completely distinct from the results of the two affected children (1.3 and less than 0.1 u/g protein). With fructose-1,6-bisphosphate as subtrate, the 96% confidence limits are 10 to 324 u/g protein and the values for the two affected children, 23.7 and 9.3 u/g. Among the nonaffected children two mucosal biopsies with F1PA activities less than 1.55 u/g were found. In one mucosal biopsy among the nonaffected children an FBPA activity less than 10 u/g was recorded. The data are interpreted as indicating that the determination of F1PA activity in intestinal mucosa is a highly sensitive test in detecting individuals with HFI. However, the specifity of the test is not absolute. Diagnosis should be based on both clinical and laboratory considerations. The determination of FBPA activity in the same biopsy specimen does not contribute substantially to the differential diagnosis.