A novel selenocystine-beta-cyclodextrin conjugate that acts as a glutathione peroxidase mimic

A novel artificial glutathione peroxidase mimic consisting of a selenocysti ne-di-beta-cyclodextrin conjugate (selenium-bridged-6,6'-amino-selenocystin e-6,6'-deoxy-di-beta-cyclodextrin) in which selenocystine is bound to the p rimary side of beta-cyclodextrin through the two amino nitrogen groups of s elenocystine, was synthesized. The glutathione peroxidase activities of the mimic-catalyzed reduction of H2O2, tert-butylhydroperoxide, and cumene hyd roperoxide by glutathione are 4.1, 2.11, and 5.82 units/mu mol, respectivel y. The first activity was 82 and 4.2 times as much as that of selenocystein e and ebselen, respectively. Studies on the effect of substrate binding on the glutathione peroxidase activity suggest that it is important to conside r substrate binding in designing glutathione peroxidase mimics. The detaile d steady-state kinetic studies showed that the mimic-catalyzed reduction of H2O2 by glutathione followed a ping-pong mechanism, which was similar to t hat of the native glutathione peroxidase.