Primary Structure of Human Plasma Glutathione Peroxidase Deduced From cDNA Sequences

Abstract

Abstract Human plasma glutathione peroxidase (GSHPx) has been shown to be a selenium-containing enzyme immunologically distinct from cellular GSHPx. Oligonucleotide probes, based on a partial amino acid sequence of one peptide in a lysine endopeptidase-digest of the purified enzyme, were used to screen a human placenta cDNA library. Nucleotide sequence analysis of the obtained clones revealed that GSHPx consisted of a 678-base pair open reading frame coding for a 226-amino acid polypeptide. The in-frame TGA codon observed at positions 217–219 was assigned to selenocysteine. The amino acid sequence exhibited only 44% homology with that of human cellular GSHPx. Northern blot analysis revealed a single transcript of 2.2 kilobases in the poly (A)+ RNA fractions of human placenta and HepG2 (human hepatic cell line), but not that of human liver. The transcript was also detected in rat kidney, but not in rat liver, lung, heart and brain.