Separation of isoenzymes of glucose-6-phosphate dehydrogenase from human erythrocytes by two-dimensional gel electrophoresis.

Isoelectric focusing performed in 6.0% polyacrylamide gel in the presence of 1.0 M urea separates well the various molecular forms of glucose-6-phosphate dehydrogenase from human erythrocytes. At least seven sharp bands appear in the gel pattern, which vary both in isoelectric points and in the relative intensity. Their isoelectric points are at pH 6.88 for band 1, pH 6.79 for band 2, pH 6.64 for band 3, pH 6.50 for band 4, pH 6.39 for band 5, pH 6.19 for band 6, and pH 6.10 for band 7. A second-dimensional disc electrophoresis performed in a polyacrylamide gel slab resolves each band into two components, a slow and a fast component defined according to their mobilities in the disc gel. The slow component constitutes the major portion of each band. All the seven slow components appear to be dimer having a molecular weight between 98,000-94,000. They belong to "change isomers" having identical molecular size but containing different net changes. The molecular weight of the fast components is between 66,800-50,600. These fast components might be monomer or the digested products of slow components.