PMID- 24972312
OWN - NLM
STAT- MEDLINE
DCOM- 20140926
LR  - 20140805
IS  - 1520-4995 (Electronic)
IS  - 0006-2960 (Linking)
VI  - 53
IP  - 30
DP  - 2014 Aug 5
TI  - Evidence of the direct involvement of the substrate TCP radical in functional 
      switching from oxyferrous O2 carrier to ferric peroxidase in the dual-function 
      hemoglobin/dehaloperoxidase from Amphitrite ornata.
PG  - 4956-69
LID - 10.1021/bi5002757 [doi]
AB  - The coelomic O2-binding hemoglobin dehaloperoxidase (DHP) from the sea worm 
      Amphitrite ornata is a dual-function heme protein that also possesses a 
      peroxidase activity. Two different starting oxidation states are required for 
      reversible O2 binding (ferrous) and peroxidase (ferric) activity, bringing into 
      question how DHP manages the two functions. In our previous study, the copresence 
      of substrate 2,4,6-trichlorophenol (TCP) and H2O2 was found to be essential for 
      the conversion of oxy-DHP to enzymatically active ferric DHP. On the basis of 
      that study, a functional switching mechanism involving substrate radicals 
      (TCP(*)) was proposed. To further support this mechanism, herein we report 
      details of our investigations into the H2O2-mediated conversion of oxy-DHP to the 
      ferric or ferryl ([TCP] < [H2O2]) state triggered by both biologically relevant 
      [TCP and 4-bromophenol (4-BP)] and nonrelevant (ferrocyanide) compounds. At <50 
      muM H2O2, all of these conversion reactions are completely inhibited by ferric 
      heme ligands (KCN and imidazole), indicating the involvement of ferric DHP. 
      Furthermore, the spin-trapping reagent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) 
      effectively inhibits the TCP/4-BP (but not ferrocyanide)-triggered conversion of 
      oxy-DHP to ferric DHP. These results and O2 concentration-dependent conversion 
      rates observed in this study demonstrate that substrate TCP triggers the 
      conversion of oxy-DHP to a peroxidase by TCP(*) oxidation of the deoxyferrous 
      state. TCP(*) is progressively generated, by increasingly produced amounts of 
      ferric DHP, upon H2O2 oxidation of TCP catalyzed initially by trace amounts of 
      ferric enzyme present in the oxy-DHP sample. The data presented herein further 
      address the mechanism of how the halophenolic substrate triggers the conversion 
      of hemoglobin DHP into a peroxidase.
FAU - Sun, Shengfang
AU  - Sun S
AD  - Department of Chemistry and Biochemistry, University of South Carolina , 
      Columbia, South Carolina 29208, United States.
FAU - Sono, Masanori
AU  - Sono M
FAU - Du, Jing
AU  - Du J
FAU - Dawson, John H
AU  - Dawson JH
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20140728
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Chlorophenols)
RN  - 0 (Ferric Compounds)
RN  - 0 (Hemoglobins)
RN  - EC 1.11.1.7 (Peroxidase)
RN  - MHS8C5BAUZ (2,4,6-trichlorophenol)
RN  - S88TT14065 (Oxygen)
SB  - IM
MH  - Animals
MH  - Chlorophenols/*chemistry
MH  - Ferric Compounds/*chemistry
MH  - Hemoglobins/*chemistry/physiology
MH  - Oxygen/*chemistry/physiology
MH  - Peroxidase/*chemistry/physiology
MH  - Polychaeta
MH  - Substrate Specificity
EDAT- 2014/06/28 06:00
MHDA- 2014/09/27 06:00
CRDT- 2014/06/28 06:00
PHST- 2014/06/28 06:00 [entrez]
PHST- 2014/06/28 06:00 [pubmed]
PHST- 2014/09/27 06:00 [medline]
AID - 10.1021/bi5002757 [doi]
PST - ppublish
SO  - Biochemistry. 2014 Aug 5;53(30):4956-69. doi: 10.1021/bi5002757. Epub 2014 Jul 
      28.