Glucose‐6‐Phosphate Dehydrogenase Johannesburg: A New Variant with Reduced Activity in a Patient with Congenital Non‐spherocytic Haemolytic Anaemia

Summary. A new variant of the red‐cell enzyme glucose‐6‐phosphate dehydrogenase has been found in a Caucasoid woman and her 5‐yr‐old son. Both presented with congenital non‐spherocytic haemolytic anaemia. The variant was found to have reduced activity and greatly increased thermolability. The enzyme was unstable even in the cold; glycerol was found to stabilize it during purification. The Michaelis constant for glucose‐6‐phosphate was found to be higher than normal, whilst that for NADP was slightly lower than normal. Electrophoretic mobility was slightly decreased. Utilization of 2‐deoxy‐glucose‐6‐phosphate and deamino‐NADP, and the shape of the pH‐activity curve, were normal.