A novel artificial glutathione peroxidase mimic consisting of a selenocystine-di-
-cyclodextrin conjugate(selenium-bridged-6,6'-amino-selenocystine-6,6'-deoxy-di-
-cyclodextrin), in which selenocystine isbound to the primary side of
-cyclodextrin through the two amino nitrogen groups of selenocystine,was synthesized. The glutathione peroxidase activities of the mimic-catalyzed reduction of H
2O
2,
tert-butylhydroperoxide, and cumene hydroperoxide by glutathione are 4.1, 2.11, and 5.82 units/
mol,respectively. The first activity was 82 and 4.2 times as much as that of selenocysteine and ebselen,respectively. Studies on the effect of substrate binding on the glutathione peroxidase activity suggestthat it is important to consider substrate binding in designing glutathione peroxidase mimics. Thedetailed steady-state kinetic studies showed that the mimic-catalyzed reduction of H
2O
2 by glutathionefollowed a ping-pong mechanism, which was similar to that of the native glutathione peroxidase.