A radioisotopic method for fructose-1-phosphate aldolase assay that facilitates diagnosis of hereditary fructose intolerance.

A sensitive new method in which D-[U-14C]fructose-1-phosphate is used for fructose-bisphosphate aldolase (EC 2.1.2.13) assay is described. The radioactive fructose-1-phosphate compound was prepared from [U-14C]fructose by use of partly purified fructokinase (EC 2.7.1.4). With this method we measured normal values for aldolase in human liver (2.4-10.0 nmol/min per mg of protein), kidney (3.6-3.8), and intestine (4.2-10.0) as well as Km values for fructose-1-phosphate (approximately 1.0-2.2 mmol/L). In patients with hereditary fructose intolerance the aldolase activity in liver and intestine was less than 10% of normal values. The Lineweaver-Burk plots for data from patients with hereditary fructose intolerance were hyperbolic, indicating a structural alteration in the enzyme.