PMID- 23865454
OWN - NLM
STAT- MEDLINE
DCOM- 20131112
LR  - 20211021
IS  - 1520-4995 (Electronic)
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 52
IP  - 32
DP  - 2013 Aug 13
TI  - Selenocysteine confers resistance to inactivation by oxidation in thioredoxin 
      reductase: comparison of selenium and sulfur enzymes.
PG  - 5472-81
LID - 10.1021/bi400462j [doi]
AB  - Mammalian thioredoxin reductase (TR) is a selenocysteine (Sec)-containing 
      homodimeric pyridine nucleotide oxidoreductase which catalyzes the reduction of 
      oxidized thioredoxin. We have previously demonstrated the full-length 
      mitochondrial mammalian TR (mTR3) enzyme to be resistant to inactivation from 
      exposure to 50 mM H2O2. Because a Sec residue oxidizes more rapidly than a 
      cysteine (Cys) residue, it has been previously thought that Sec-containing 
      enzymes are "sensitive to oxidation" compared to Cys-orthologues. Here we show 
      for the first time a direct comparison of the abilities of Sec-containing mTR3 
      and the Cys-orthologue from D. melanogaster (DmTR) to resist inactivation by 
      oxidation from a variety of oxidants including H2O2, hydroxyl radical, 
      peroxynitrite, hypochlorous acid, hypobromous acid, and hypothiocyanous acid. The 
      results show that the Sec-containing TR is far superior to the Cys-orthologue TR 
      in resisting inactivation by oxidation. To further test our hypothesis that the 
      use of Sec confers strong resistance to inactivation by oxidation, we constructed 
      a chimeric enzyme in which we replaced the active site Cys nucleophile of DmTR 
      with a Sec residue using semisynthesis. The chimeric Sec-containing enzyme has 
      similar ability to resist inactivation by oxidation as the wild type 
      Sec-containing TR from mouse mitochondria. The use of Sec in the chimeric enzyme 
      "rescued" the enzyme from oxidant-induced inactivation for all of the oxidants 
      tested in this study, in direct contrast to previous understanding. We discuss 
      two possibilities for this rescue effect from inactivation under identical 
      conditions of oxidative stress: (i) Sec resists overoxidation and inactivation, 
      whereas a Cys residue can be permanently overoxidized to the sulfinic acid form, 
      and (ii) Sec protects the body of the enzyme from harmful oxidation by allowing 
      the enzyme to metabolize (turnover) various oxidants much better than a 
      Cys-containing TR.
FAU - Snider, Gregg W
AU  - Snider GW
AD  - Department of Biochemistry, University of Vermont, 89 Beaumont Ave, Given 
      Building Room B413, Burlington, VT 05405, USA.
FAU - Ruggles, Erik
AU  - Ruggles E
FAU - Khan, Nadeem
AU  - Khan N
FAU - Hondal, Robert J
AU  - Hondal RJ
LA  - eng
GR  - R01 GM094172/GM/NIGMS NIH HHS/United States
GR  - GM094172/GM/NIGMS NIH HHS/United States
PT  - Comparative Study
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
DEP - 20130731
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Thiocyanates)
RN  - 0 (hypothiocyanous acid)
RN  - 0CH9049VIS (Selenocysteine)
RN  - 70FD1KFU70 (Sulfur)
RN  - BBX060AN9V (Hydrogen Peroxide)
RN  - EC 1.8.1.9 (Thioredoxin-Disulfide Reductase)
SB  - IM
MH  - Animals
MH  - Catalysis
MH  - Drosophila melanogaster/enzymology/metabolism
MH  - Hydrogen Peroxide
MH  - Kinetics
MH  - Mice
MH  - Oxidation-Reduction
MH  - Selenocysteine/chemistry/*metabolism
MH  - Sulfur/metabolism
MH  - Thiocyanates
MH  - Thioredoxin-Disulfide Reductase/chemistry/*metabolism
PMC - PMC3760785
MID - NIHMS508375
EDAT- 2013/07/20 06:00
MHDA- 2013/11/13 06:00
PMCR- 2014/08/13
CRDT- 2013/07/20 06:00
PHST- 2013/07/20 06:00 [entrez]
PHST- 2013/07/20 06:00 [pubmed]
PHST- 2013/11/13 06:00 [medline]
PHST- 2014/08/13 00:00 [pmc-release]
AID - 10.1021/bi400462j [doi]
PST - ppublish
SO  - Biochemistry. 2013 Aug 13;52(32):5472-81. doi: 10.1021/bi400462j. Epub 2013 Jul 
      31.