Human Glucose‐6‐Phosphate Dehydrogenase: Purification of the Erythrocyte Enzyme and the Influence of Ions on its Activity

Normal glucose‐6‐phosphate dehydrogenase from human erythrocytes has been purified 70,000‐fold from haemolysates with an overall yield of 30%. Bulk fractionation was carried out on DEAE‐ and CM‐Sephadex. Gradient elution was performed on DEAE‐ and CM‐Sephadex, and gel filtration on Sephadex G‐200. Ammonium sulphate precipitation was used after CM‐Sephadex and G‐200 steps. The final preparation had a specific activity of 180 units/mg, and ultracentrifugation and electrophoresis showed that it was homogeneous. The purification procedure was completed in 3 weeks and gave 20 mg of purified enzyme from 30 litres of blood. The activity of the enzyme varied with the ionic strength of the medium. The implications of the ionic strength dependence of enzyme activity are discussed.