ACTIVE-SITE MODEL PEPTIDES OF GLUTATHIONE-PEROXIDASE - A SE-77 NMR-STUDY

To test the feasibility of using Se-77 NMR to distinguish between different proposed mechanisms of action of the selenoenzyme glutathion peroxidase, active site model peptides containing a selenocysteine residue have been synthesized and their H-1 and Se-77 NMR spectra recorded. It was found that oxidation of the reduced form selenol by hydroperoxide in the presence of thiol gives cyclic selenenamide and diselenide. Selenenic and seleninic acid, thioseleninate and seleninamide species have not be evidenced during this reaction. Reduction of the cyclic selenenamide by thiol yields selenenyl sulfide and diselenide. The selenol form has not been observed in this case.