Purification and properties of glutathione peroxidase from human placenta.
Glutathione peroxidase (glutathione--H2O2 oxidoreductase; EC 1.11.1.9) was purified to homogeneity from human placenta by using (NH4)2SO4 precipitation, ion-exchange chromatography, Sephadex gel filtration and preparative polyacrylamide-disc-gel electrophoresis. Glutathione peroxidase from human placenta is a tetramer, having 4g-atoms of selenium/mol of protein. The molecular weight of the enzyme is about 85000 with a subunit size of about 22,000. Kinetic properties of the enzyme are described. On incubation with cyanide, glutathione peroxidase is completely and irreversibly inactivated and selenium is released as a low-molecular-weight fragment. Reduced glutathione, beta-mercaptoethanol and dithiothreitol protect the enzyme from inactivation by cyanide and the release of selenium. Properties of human placental glutathione peroxidase are similar to those of isoenzyme A reported earlier by us from human erythrocytes. The presence of isoenzyme, B, reported earlier by us in human erythrocytes, was not detected in placenta. Also selenium-independent glutathione peroxidase (isoenzyme II), which is specific for cumene hydroperoxide, was not present in human placenta.
D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003486:Cyanides / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005979:Glutathione Peroxidase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008970:Molecular Weight; D010544:Peroxidases / Q000378:metabolism*; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D012643:Selenium / Q000378:metabolism
D003486:Cyanides; D010544:Peroxidases; D005979:Glutathione Peroxidase; D012643:Selenium