Human Thioredoxin Reductase Directly Reduces Lipid Hydroperoxides by NADPH and Selenocystine Strongly Stimulates the Reaction via Catalytically Generated Selenols

doi:10.1074/jbc.270.20.11761

Human Thioredoxin Reductase Directly Reduces Lipid Hydroperoxides by NADPH and Selenocystine Strongly Stimulates the Reaction via Catalytically Generated Selenols(*)

From the (1) Medical Nobel Institute for Biochemistry and the
(2) Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden

^§To whom correspondence should be addressed. Tel.: 46-8-728 76 86; Fax: 46-8-728 47 16.

Abstract

Human placenta thioredoxin reductase (HP-TR) in the presence of NADPH-catalyzed reduction of (15S)-hydroperoxy-(5Z),(8Z),11(Z),13(E)-eicosatetraenoic acid ((15S)-HPETE) into the corresponding alcohol ((15S)-HETE). Incubation of 50 nM HP-TR and 0.5 mM NADPH with 300 μM 15-HPETE for 5 min resulted in formation of 16.5 μM 15-HETE. After 60 min, 74.7 μM 15-HPETE was reduced. The rate of the reduction of 15-HPETE by the HP-TR/NADPH peroxidase system was increased 8-fold by the presence of 2.5 μM selenocystine, a diselenide amino acid. In this case, 15-HPETE was catalytically reduced by the selenol amino acid, selenocysteine, generated from the diselenide by the HP-TR/NADPH system. To a smaller extent, selenodiglutathione or human thioredoxin also potentiated the reduction of 15-HPETE by HP-TR. Hydrogen peroxide and 15-HPETE were reduced at approximately the same rate by HP-TR, thioredoxin, and selenocystine. In contrast, t-butyl hydroperoxide was reduced at a 10-fold lower rate. Our data suggest two novel pathways for the reduction and detoxification of lipid hydroperoxides, hydrogen peroxide, and organic hydroperoxides, i.e. the human thioredoxin reductase-dependent pathway and a coupled reduction in the presence of selenols or selenide resulting from the reduction of selenocystine or selenodiglutathione.

Footnotes

↵* This investigation was supported by grants from the Karolinska Institute, the Swedish Cancer Society (961), the Swedish Medical Research Council (13X-3529 and 13X-05170), and Knut och Alice Wallenbergs Stiftelse. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

HPETE

hydroperoxyeicosatetraenoic acid

HETE

hydroxyeicosatetraenoic acid

TR

thioredoxin reductase

Trx

thioredoxin

HP-TR

human placenta thioredoxin reductase

CT-TR

calf thymus thioredoxin reductase

HPLC

high performance liquid chromatography

GS-Se-SG

selenodiglutathione

GR

glutathione reductase

GSH-Px

glutathione peroxidase.
↵²M. Björnstedt, M. Hamberg, and A. Holmgren, manuscript in preparation.