DEFICIENCY OF GLUCOSE-6-PHOSPHATE-DEHYDROGENASE FOUND IN A CASE OF HEPATIC FRUCTOSE-1,6-DIPHOSPHATASE DEFICIENCY

The first case of fructose-1,6-diphosphatase (FDPase) deficiency in Japan showed a decreased activity of glucose-6-phos- phate dehydrogenase (G6PD) in the liver, white, and red blood cells. In the enzymatic study of G6PD which was partially purified from red cells, the following characteristics were observed in the enzyme of the patient. 1) The G6PD activity of the patient was reduced to 17% of normal, but no evidence of a hemolytic episode was found in his past and family history. 2) In the investigation of G6PD of the patient, no abnormalities were observed in its enzymatic parameters such as electrophoretic mobility, Km for G6P and NADP, Ki for NADPH, the utilization of 2-deoxy G6P and deamino NADP, heat-stability, and pH curves. 3) The dissociation constants of red blood cell G6PD for NADP and NADPH, which were obtained from the investigations on the reactivation of cold- inactivated G6PD at 37°C, were about 3 times higher in the patient as compared to the values of the normal controls. Based on these findings, it might be concluded that the G6PD deficiency found in the red blood cells of this case of a FDPase deficiency is a unique variant, which could not be characterized by using only the method recommended by a World Health Organization (WHO) scientific group. Considering that the abnormality observed in the G6PD of this patient was a decrease in the affinity of the enzyme for its coenzymes, the dissociation constants for the coenzymes in reactivation process might be another important kinetic parameter in characterizing the G6PD deficiency. Speculation: The red cell G6PD of a case of FDPase deficiency showed a decreased enzymatic activity and a lowered affinity for its coenzymes in reactivation process. Although it is strongly suggested that these two rare enzyme deficiencies take place in an individual coincidentally, a possible relationship of the two enzyme deficiencies should be considered. Further studies on these enzyme deficiencies now appear necessary to learn more about this association. © 1979 International Pediatric Research Foundation, Inc.