Properties of glutathione peroxidase from the hepatopancreas of freshwaterprawn Macrobrachium malcolmsonii

Oxidative stress stimulates production of hydrogen peroxide and organic hyd roperoxides which are involved in lipid peroxidation and oxidative damage t o protein. Glutathione peroxidase protects against oxidative stress. Quanti tative data on glutathione peroxidase of crustaceans are very limited and s o this study was performed to determine the assay condition of glutathione peroxidase in crustaceans. Particularly, some properties of hepatic seleniu m dependent glutathione peroxidase and total glutathione peroxidase of the freshwater prawn Macrobrachium malcolmsonii were examined. The optimal pH f or Se-GSH-Px was 7.5 and for total GSH-Px was 8.0. The activation energy (E -a) was found to be 9.14 Kcal/mol for Se-GSH-Px and 10.96 Kcal/mol for tota l GSH-Px. The energy inhibition (E-i) value for Se-GSH-Px was 14.36 Kcal/mo l and 13.71 Kcal/mol for total GSH-Px. The Km values a ere also determined at various concentrations of substrates (GSH, CHP, H2O2) for both enzymes. (C) 1999 Elsevier Science Ltd. All rights reserved.