Glutathione Reductase from Human Erythrocytes

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Abstract
Glutathione reductase from human erythrocytes exists predominantly as an entity of 100000 molecular weight under various conditions of pH and ionic strength. The s20,w of 5.5 S and D20,w of 50 μm2/s correlate with the molecular weight determined by sedimentation equilibrium. The homogeneity of this species is primarily dependent on the presence of thiols and secondarily on high concentrations of salt. The amino‐acid composition of the enzyme shows similarities both with glutathione reductases from other sources and with lipoamide dehydrogenase. From the flavin content and dodecylsulphate‐polyacrylamide electrophoresis it is inferred that the native enzyme is a dimer composed of similar subunits of 50000 molecular weight. In the absence of thiols, glutathione reductase shows a tendency to form tetramers and larger aggregates. Although these larger species are also catalytically active, under cellular conditions the presence of its product, reduced glutathione, should maintain the enzyme as the dimeric entity.