Purification and characterization of genetic variants of 6-phosphogluconate dehydrogenase

Abstract

This paper describes the physicochemical characteristics in partially purified enzyme on subjects with the Pd A, Pd AB, and Pd B variants of 6-phosphogluconic dehydrogenase (6PGD). For these studies, whole blood was purified about 225-fold using ion exchange chromatography on DEAE cellulose column and fractionation with ammonium sulfate. 6PGD emerges as a single peak between 0.01 m and 0.1 m phosphate buffer on the column and is precipitated in the 55–80% fraction of ammonium sulfate. This purified enzyme can be stored frozen for several months without appreciable loss of activity and contains no detectable activity of glucose 6-phosphate dehydrogenase and glutathione reductase. The three variants of partially purified 6PGD varied from each other in two respects. The transitional temperature is 47.8 C for Pd A, 45.4 C for Pd AB, and 41.1 C for Pd B. The K _m for 6PGA is 30 μm for Pd A, 21 μm for Pd AB, and 15 μmfor Pd B. These observations add further strength to the concept that the polymorphism in 6PGD represents alterations in either the configuration or structure of the protein molecule itself.