Membrane Characteristics and Metabolic Properties of Glucose‐6‐Phosphate Dehydrogenase Deficient Red Cells

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Abstract
Summary. Two Finnish variants of reduced erythrocyte glucose‐dehydrogenase (G‐6‐PD) activity were studied. The G‐6‐PD Espoo variant is characterized by severe enzyme deficiency which is normally non‐haemolytic although primaquine sensitive. The other variant, G‐6‐PD Helsinki, in which the enzyme activity is moderately reduced, is associated with chronic haemolytic anaemia.The activity of the pentose phosphate pathway was not stimulated by methylene blue in G‐6‐PD Espoo cells, whereas in normal and G‐6‐PD Helsinki cells there were increases in shunt activity of 64.5‐ and 5.3‐fold, respectively. As judged by the accumulation of 6‐phosphogluconate after incubation with 6‐aminonicotinamide, the activity of the pentosc phosphate pathway was similar in normal and G‐6‐PD Helsinki cells, whereas in G‐6‐PD Espoo cells the metabolic flux through this pathway was decreased. Quantities of sulphydryl groups in intact cells and isolated membranes were similar in normal and G‐6‐PD deficient cells, as revealed by spin label experiments. In contrast to the situation in normal cells, sulphydryl groups in G‐6‐PD Espoo cells, and to a lesser extent in G‐6‐PD Helsinki cells, were sensitive to oxidation by acetylphenylhydrazine. In the G‐6‐PD Helsinki cells, but not in the G‐6‐PD Espoo cells, membrane fluidity was increased, as judged from the increased mobility of the stearic acid spin label.Mechanisms are discussed by which G‐6‐PD deficient cells retain adequate levels of NADPH during resting conditions, and it is suggested that the chronic haemolysis associated with G‐6‐PD Helsinki could be due to a defect in the lipid region of the cell membrane.