A new variant of glucosephosphate isomerase deficiency (GPI-Utrecht)

A new case of glucosephosphate isomerase deficiency is described in a Dutch family. The activity of the enzyme was decreased to 20–25% of the normal value. Characterization of the defect enzyme showed a pronounced thermolability. Heating of the enzyme at 45°C showed a loss of activity of 90% after one hour. The pH-optimum and the electrophoretic migration were normal. The Km-value for F-6-P, the Ki for the competitive inhibitors 2,3-DPG and 6-PG were in the normal range. The variant described here differs from all known variant