Bioelectrocatalysis by a selenoenzyme

Electron transfer between the selenoprotein phospholipid hydroperoxide glutathione peroxidase and gold electrodes covered by a self assembled monolayer of mercaptoundecanoic acid was achieved for the first time. Selenenic acid, the oxidized enzyme form, which is generated by the reaction with peroxide, was not reduced at the electrode. A reduction current is obtained only in the presence of both peroxide and the second substrate glutathione. This suggests the selenadisulfide intermediate as the electroactive species. The reaction was only possible with the monomeric phospholipid hydroperoxide glutathione peroxidase while the tetrameric cytosolic glutathione peroxidase did not react. (C) 1998 Elsevier Science S.A. All rights reserved.