Rat liver glutathione peroxidase: Purification and study of multiple forms

The subcellular distributions of glutathione peroxidase and ⁷⁵Se in rat liver were determined. Approximately 75% of the enzyme and 58% of the ⁷³Se were contained in the cytosolic fraction. Rat liver cytosol glutathione peroxidase was purified 1029-fold from homogenate to yield a sample with a specific activity of 278 μmol of NADPH oxidized/ min/mg of protein. The purified enzyme was subjected to disc-gel and sodium dodecyl sulfate-disc-gel electrophoresis, which confirmed the purity of the enzyme as well as the existence of multiple electrophoretic forms. Glutathione peroxidase existed as a large aggregate after homogenization, and means of dissociating the aggregate were investigated. The enzyme was isolated as a neutrally charged protein and became negatively charged upon storage, a phenomenon that was independent of the aggregation.