Chronic nonspherocytic hemolytic anemia (CNSHA) and glucose 6 phosphate dehydrogenase (G6PD) deficiency in a patient with familial amyloidotic polyneuropathy (FAP). Molecular study of a new variant (G6PD Clinic) with markedly acidic pH optimum.
A new glucose-6-phosphate dehydrogenase ( G6PD ) variant with severe erythrocytic G6PD deficiency and a unique pH optimum is described in a young patient with chronic nonspherocytic hemolytic anemia ( CNSHA ) and familial amyloidotic polyneuropathy ( FAP ) . Chronic hemolysis was present in the absence of infections , oxidant drugs or ingestion of faba beans . Residual enzyme activity was about 2 . 6 % and 63 % of normal activity in erythrocytes and leucocytes , respectively . A molecular study using standard methods showed G6PD in the patient to have normal electrophoretic mobility ( at pH 7 . 0 , 8 . 0 and 8 . 8 ) , normal apparent affinity for substrates ( Km , G6P and NADP ) and a slightly abnormal utilization of substrate analogues ( decreased deamino-NADP and increased 2-deoxyglucose-6-phosphate utilization ) . Heat stability was found to be markedly decreased ( 8 % of residual activity after 20 min of incubation at 46 degrees C ) and a particular characteristic of this enzyme was a biphasic pH curve with a greatly increased activity at low pH . Although molecular characteristics of this variant closely resemble those of G6PD Bangkok and G6PD Duarte , it can be distinguished from these and all other previously reported variants by virtue of its unusual pH curve . Therefore the present variant has been designated G6PD Clinic to distinguish it from other G6PD variants previously described
