Anomalous behavior of glutathione reductase on dilution

Serum glutathione reductase activity decreases on standing at room temperature. Dilution of the sample slows this decay in sera from patients with a variety of clinical disorders, and reverses the inactivation in sera from patients with liver or biliary tract disease. Prolonged contact with dithioeythritol or acetate buffer, pH 6.4, at 4 degrees C prevents spontaneous inactivation of the native serum and abolishes the effect of dilution. These hitherto unreported phenomena are a source of potential inaccuracy in assays for this enzyme. The inactivation may be the result of conformational folding with "burying" of active sites, or of molecular aggregation brought about by hydrogen bonding or disulfide bond formation.