Thalassemia-like abnormalities of the red cell membrane in hemoglobin E trait and disease

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Abstract
In recent studies, we observed a decrease of KMapp, an abnormally biphasic kinetics of the red cell membrane neutral phosphatase and an increased binding of hemoglobin to the membrane in various forms of β-thalassemia. Since the gene encoding the β chain (βE chain) of hemoglobin E (HbE) is endowed with some thalassemic characteristics, we studied the erythrocyte membrane in 25 individuals with Hb E trait or disease. The apparent Michaelis-Menten constant for p-nitrophenylphosphate (the artificial substrate used) was significantly decreased, as in β-thalassemia. However, the kinetics was monophasic in all the heterozygotes and in four of the homozygotes. It was biphasic only in the three other homozygotes. Vmax was also significantly reduced, a fact that is masked, when not reversed in β-thalassemia, owing to the rejuvenation of the red cell population. In 5 mM phosphate buffer (pH 8.00), the binding of Hb E to the erythrocyte ghosts was increased in the homozygotes. In the heterozygotes, Hb A binding was also increased, as is the case in β-thalassemia. This latter fact suggests that the membrane binding site(s) of hemoglobin is (are) altered. We found a highly significant increase of Hb F in EE subjects. The present study extends to the red cell membrane the β-thalassemic phenotype associated with the βE gene.