Serine incorporation into the selenocysteine moiety of glutathione peroxidase.

摘要: The selenium in mammalian glutathione peroxidase is present as a selenocysteine ([Se]Cys) moiety incorporated into the peptide backbone 41-47 residues from N-terminal end. To study origin of skeleton [Se]Cys moiety, we perfused isolated rat liver with 14C- or 3H-labeled amino acids for 4 h, purified GSH peroxidase, derivatized to carboxymethylselenocysteine ([Se]Cys(Cm)), and determined acid specific activity. Perfusion [14C]cystine resulted incorporation without labeling [Se]Cys(Cm), indicating that cysteine not direct precursor [Se]Cys. [14C]Serine perfusion labeled serine, glycine (the serine hydroxymethyltransferase product), [Se]Cys(Cm) whereas [3-3H]serine only thus demonstrating derived serine. similar activities strongly suggest pool used [Se] Cys synthesis same acylation seryl-tRNAs.