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Cyclometalated Ruthenium(II) Complexes As Efficient Redox Mediators in Peroxidase Catalysis

Alpeeva, I; Sukharev, V; Alexandrova, L; Shilova, N; Bovin, N; Csöregi, Elisabeth LU ; Ryabov, A and Sakharov, I (2003) In Journal of Biological Inorganic Chemistry 8(6). p.683-688
Abstract
Cyclometalated ruthenium(II) complexes, [Ru II(C~N)(N~N) 2]PF 6 [HC~N=2-phenylpyridine (Hphpy) or 2-(4'-tolyl)pyridine; N~N=2,2'-bipyridine, 1,10-phenanthroline, or 4,4'-dimethyl-2,2'-bipyridine], are rapidly oxidized by H 2O 2 catalyzed by plant peroxidases to the corresponding Ru III species. The commercial isoenzyme C of horseradish peroxidase (HRP-C) and two recently purified peroxidases from sweet potato (SPP) and royal palm tree (RPTP) have been used. The most favorable conditions for the oxidation have been evaluated by varying the pH, buffer, and H 2O 2 concentrations and the apparent second-order rate constants ( k app) have been measured. All the complexes studied are oxidized by HRP-C at similar rates and the rate constants k... (More)
Cyclometalated ruthenium(II) complexes, [Ru II(C~N)(N~N) 2]PF 6 [HC~N=2-phenylpyridine (Hphpy) or 2-(4'-tolyl)pyridine; N~N=2,2'-bipyridine, 1,10-phenanthroline, or 4,4'-dimethyl-2,2'-bipyridine], are rapidly oxidized by H 2O 2 catalyzed by plant peroxidases to the corresponding Ru III species. The commercial isoenzyme C of horseradish peroxidase (HRP-C) and two recently purified peroxidases from sweet potato (SPP) and royal palm tree (RPTP) have been used. The most favorable conditions for the oxidation have been evaluated by varying the pH, buffer, and H 2O 2 concentrations and the apparent second-order rate constants ( k app) have been measured. All the complexes studied are oxidized by HRP-C at similar rates and the rate constants k app are identical to those known for the best substrates of HRP-C (10 6–10 7 M -1 s -1). Both cationic (HRP-C) and anionic (SPP and RPTP) peroxidases show similar catalytic efficiency in the oxidation of the Ru II complexes. The mediating capacity of the complexes has been evaluated using the SPP-catalyzed co-oxidation of [Ru II(phpy)(bpy) 2]PF 6 and catechol as a poor peroxidase substrate as an example. The rate of enzyme-catalyzed oxidation of catechol increases more than 10,000-fold in the presence of the ruthenium complex. A simple routine for calculating the rate constant k c for the oxidation of catechol by the Ru III complex generated enzymatically from [Ru II(phpy)(bpy) 2] + is proposed. It is based on the accepted mechanism of peroxidase catalysis and involves spectrophotometric measurements of the limiting Ru II concentration at different concentrations of catechol. The calculated k c value of 0.75 M -1 s -1 shows that the cyclometalated Ru II complexes are efficient mediators in peroxidase catalysis. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Biological Inorganic Chemistry
volume
8
issue
6
pages
683 - 688
publisher
Springer
external identifiers
  • wos:000184294700011
  • pmid:12774217
  • scopus:0041654791
ISSN
1432-1327
DOI
10.1007/s00775-003-0467-2
language
English
LU publication?
yes
id
0a64a06c-bb2d-4400-b7f9-6157406362d8 (old id 129033)
date added to LUP
2007-06-29 15:32:14
date last changed
2017-01-01 04:30:26
@article{0a64a06c-bb2d-4400-b7f9-6157406362d8,
  abstract     = {Cyclometalated ruthenium(II) complexes, [Ru II(C~N)(N~N) 2]PF 6 [HC~N=2-phenylpyridine (Hphpy) or 2-(4'-tolyl)pyridine; N~N=2,2'-bipyridine, 1,10-phenanthroline, or 4,4'-dimethyl-2,2'-bipyridine], are rapidly oxidized by H 2O 2 catalyzed by plant peroxidases to the corresponding Ru III species. The commercial isoenzyme C of horseradish peroxidase (HRP-C) and two recently purified peroxidases from sweet potato (SPP) and royal palm tree (RPTP) have been used. The most favorable conditions for the oxidation have been evaluated by varying the pH, buffer, and H 2O 2 concentrations and the apparent second-order rate constants ( k app) have been measured. All the complexes studied are oxidized by HRP-C at similar rates and the rate constants k app are identical to those known for the best substrates of HRP-C (10 6–10 7 M -1 s -1). Both cationic (HRP-C) and anionic (SPP and RPTP) peroxidases show similar catalytic efficiency in the oxidation of the Ru II complexes. The mediating capacity of the complexes has been evaluated using the SPP-catalyzed co-oxidation of [Ru II(phpy)(bpy) 2]PF 6 and catechol as a poor peroxidase substrate as an example. The rate of enzyme-catalyzed oxidation of catechol increases more than 10,000-fold in the presence of the ruthenium complex. A simple routine for calculating the rate constant k c for the oxidation of catechol by the Ru III complex generated enzymatically from [Ru II(phpy)(bpy) 2] + is proposed. It is based on the accepted mechanism of peroxidase catalysis and involves spectrophotometric measurements of the limiting Ru II concentration at different concentrations of catechol. The calculated k c value of 0.75 M -1 s -1 shows that the cyclometalated Ru II complexes are efficient mediators in peroxidase catalysis.},
  author       = {Alpeeva, I and Sukharev, V and Alexandrova, L and Shilova, N and Bovin, N and Csöregi, Elisabeth and Ryabov, A and Sakharov, I},
  issn         = {1432-1327},
  language     = {eng},
  number       = {6},
  pages        = {683--688},
  publisher    = {Springer},
  series       = {Journal of Biological Inorganic Chemistry},
  title        = {Cyclometalated Ruthenium(II) Complexes As Efficient Redox Mediators in Peroxidase Catalysis},
  url          = {http://dx.doi.org/10.1007/s00775-003-0467-2},
  volume       = {8},
  year         = {2003},
}