Selenoprotein P in human plasma as an extracellular phospholipid hydroperoxide glutathione peroxidase: Isolation and enzymatic characterization of human selenoprotein P

Yoshiro Saito, Takaaki Hayashi, Ayako Tanaka, Yasuko Watanabe, Masayo Suzuki, Eiji Saito, Kazuhiko Takahashi

Research output: Contribution to journalArticle

195 Citations (Scopus)

Abstract

Selenoprotein P is an extracellular protein containing presumably 10 selenocysteines that are encoded by the UGA stop codon in the open reading frame of the mRNA. The function of selenoprotein P is currently unknown, although several indirect lines of evidence suggest that selenoprotein P is a free radical scavenger. We first developed a conventional procedure to isolate selenoprotein P from human plasma. Next, we investigated the reactivities of selenoprotein P against various hydroperoxides in the presence of glutathione. Although selenoprotein P reduces neither hydrogen peroxide nor tertiary butyl hydroperoxide, it does reduce phospholipid hydroperoxide such as 1-palmitoyl-2-(13-hydroperoxy-cis-9,trans-11- octadecadienoyl)-3-phosphatidylcholine hydroperoxide. Kinetic analysis demonstrated a tert-uni ping-pong mechanism, similar to those described for classical glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase. Not only glutathione, but also dithiothreitol, mercaptoethanol, cysteine, and homocysteine, were effective as reducing substances, as in the case of phospholipid hydroperoxide glutathione peroxidase. These results show that selenoprotein P functions as a phospholipid hydroperoxide glutathione peroxidase in extracellular fluids.

Original languageEnglish
Pages (from-to)2866-2871
Number of pages6
JournalJournal of Biological Chemistry
Volume274
Issue number5
DOIs
Publication statusPublished - 1999 Jan 29
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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