GLUTATHIONE PEROXIDASE IN LENS AND A SOURCE OF HYDROGEN PEROXIDE IN AQUEOUS HUMOUR

Abstract

Glutathione peroxidase has been demonstrated in cattle, rabbit and guinea-pig lenses. The enzyme will oxidize GSH either with hydrogen peroxide added at the start of the reaction or with hydrogen peroxide generated enzymically with glucose oxidase. No product other than GSSG was detected. Oxidation of GSH can be coupled with oxidation of malate through the intermediate reaction of glutathione reductase and NADPH2. Traces of hydrogen peroxide are present in aqueous humor it is formed when the ascorbic acid of aqueous humor is oxidized. Hydrogen peroxide will diffuse into the explanted intact lens and oxidize the contained GSH. The additon of glucose to the medium together with hydrogen peroxide maintains the concentration of lens GSH. Glutathione peroxidase in lens extracts will couple with the oxidation of ascorbic acid. It is suggested that, as there is only weak catalase activity in lens, glutathione peroxidase may act as one link between the oxygen of the aqueous humor and NADPH2.