Glutathione peroxidase (GPX) is one of the most crucial antioxidant enzymes in a variety of organisms. Here we described a new strategy for generating a novel GPX mimic by combination of a phage-displayed random 15-mer peptide library followed by computer-aided rational design and chemical mutation. The novel GPX mimic is a homodimer consisting of a 15-mer selenopeptide with an appropriate catalytic center, a specific binding site for substrates, and high catalytic efficiency. Its steady state kinetics was also studied, and the values of k cat /K mGSH and k cat / K mH 2 O 2 were found to be similar to that of native GPX and the highest among the existing GPX mimics. Moreover, the novel GPX mimic was confirmed to have a strong antioxidant ability to inhibit lipid peroxidation by measuring the content of malondialdehyde, cell viability, and lactate dehydrogenase activity. Importantly, the novel GPX mimic can penetrate into the cell membrane because of its small molecular size. These characteristics endue the novel mimic with potential perspective for pharmaceutical applications.

A novel artificial glutathione peroxidase mimic consisting of a selenocystine-di-beta-cyclodextrin conjugate (selenium-bridged-6, 6'-amino-selenocystine-6,6'-deoxy-di-beta-cyclodextrin), in which selenocystine is bound to the primary side of beta-cyclodextrin through the two amino nitrogen groups of selenocystine, was synthesized. The glutathione peroxidase activities of the mimic-catalyzed reduction of H(2)O(2), tert-butylhydroperoxide, and cumene hydroperoxide by glutathione are 4.1, 2.11, and 5.82 units/micromol, 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 suggest that it is important to consider substrate binding in designing glutathione peroxidase mimics. The detailed steady-state kinetic studies showed that the mimic-catalyzed reduction of H(2)O(2) by glutathione followed a ping-pong mechanism, which was similar to that of the native glutathione peroxidase.

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