Characterization of two new variants of glucose-phosphate-isomerase deficiency with hereditary nonspherocytic hemolytic anemia.

Abstract

Abstract Two new patients with glucosephosphate isomerase (GPI) deficiency with nonspherocytic hemolytic anemia are described. The residual enzymes have been characterized by their biochemical properties as substrate affinity, pH optimum, heat stability, molecular weight, isoelectric point, and electrophoretic behavior. Genetic studies in the first patient indicated that he was heterozygous for two variants. One of these had no detectable activity, and is merely designated as GPI (−). The other enzyme, inherited from the patient's father, is designated as GPI Los Angeles. GPI Los Angeles manifests three bands of slowed electrophoretic mobility, an abnormally low isoelectric point, and is abnormally thermolabile. It has a normal pH optimum, K m for fructose-6-phosphate and molecular weight. The other patient appeared to have a single abnormal enzyme which was electrophoretically slow, and had a slightly lowered isoelectric point and was thermolabile. Its pH optimum and K m for fructose-6-phosphate appeared to be essentially normal.