Characterization of a new G6PD variant: G6PD Titusville.

We describe a new glucose-6-phosphate dehydrogenase mutant, G-6-PD Titusville. The propositus is a 7-month-old black male infant with a transient hemolytic episode. The mutant enzyme is characterized by abnormal electrophoretic mobility, thermolability, Km for NADP, abnormal deamino NADP use and a decreased sensitivity to inhibition by NADPH. G-6-PD activity of hemolysate, as measured under optimal in vitro conditions, was not initially decreased, whereas fibroblasts, granulocytes, and platelets showed a markedly decreased level of enzyme activity. These properties identify G6PD Titusville as a unique variant of this X-linked, housekeeping enzyme. We conclude that although the propositus with G6PD Titusville had a transient hemolytic episode, we cannot be certain whether this association was a causative one.