scholarly journals Spectroscopic characterization of cytochrome c peroxidase from Paracoccus denitrificans

1993 ◽  
Vol 294 (3) ◽  
pp. 745-752 ◽  
Author(s):  
R Gilmour ◽  
C F Goodhew ◽  
G W Pettigrew ◽  
S Prazeres ◽  
I Moura ◽  
...  
Keyword(s):  
Cytochrome C ◽  
High Spin ◽  
Spin State ◽  
Time Course ◽  
Paracoccus Denitrificans ◽  
Mixed Valence ◽  
Cytochrome C Peroxidase ◽  
High Spin State ◽  
High Potential ◽  
Intermediate Form

The cytochrome c peroxidase of Paracoccus denitrificans is similar to the well-studied enzyme from Pseudomonas aeruginosa. Like the Pseudomonas enzyme, the Paracoccus peroxidase contains two haem c groups, one high potential and one low potential. The high-potential haem acts as a source of the second electron for H2O2 reduction, and the low-potential haem acts as a peroxidatic centre. Reduction with ascorbate of the high-potential haem of the Paracoccus enzyme results in a switch of the low-potential haem to a high-spin state, as shown by visible and n.m.r. spectroscopy. This high-spin haem of the mixed-valence enzyme is accessible to ligands and binds CN- with a KD of 5 microM. The Paracoccus enzyme is significantly different from that from Pseudomonas in the time course of high-spin formation after reduction of the high-potential haem, and in the requirement for bivalent cations. Reduction with 1 mM ascorbate at pH 6 is complete within 2 min, and this is followed by a slow appearance of the high-spin state with a half-time of 10 min. Thus the process of reduction and spin state change can be easily separated in time and the intermediate form obtained. This separation is also evident in e.p.r. spectra, although the slow change involves an alteration in the low-spin ligation at this temperature rather than a change in spin state. The separation is even more striking at pH 7.5, where no high-spin form is obtained until 1 mM Ca2+ is added to the mixed-valence enzyme. The spin-state switch of the low-potential haem shifts the midpoint redox potential of the high-potential haem by 50 mV, a further indication of haem-haem interaction.

scholarly journals The kinetics of the oxidation of cytochrome c by Paracoccus cytochrome c peroxidase

1994 ◽  
Vol 300 (3) ◽  
pp. 907-914 ◽  
Author(s):  
R Gilmour ◽  
C F Goodhew ◽  
G W Pettigrew ◽  
S Prazeres ◽  
J J Moura ◽  
...  
Keyword(s):  
Cytochrome C ◽  
High Spin ◽  
Spin State ◽  
Paracoccus Denitrificans ◽  
Cytochrome C Peroxidase ◽  
High Spin State ◽  
Enzyme Activation ◽  
First Order ◽  
Ferrocytochrome C ◽  
Kinetics Of

In work that is complementary to our investigation of the spectroscopic features of the cytochrome c peroxidase from Paracoccus denitrificans [Gilmour, Goodhew, Pettigrew, Prazeres, Moura and Moura (1993) Biochem. J. 294, 745-752], we have studied the kinetics of oxidation of cytochrome c by this enzyme. The enzyme, as isolated, is in the fully oxidized form and is relatively inactive. Reduction of the high-potential haem at pH 6 with ascorbate results in partial activation of the enzyme. Full activation is achieved by addition of 1 mM CaCl2. Enzyme activation is associated with formation of a high-spin state at the oxidized low-potential haem. EGTA treatment of the oxidized enzyme prevents activation after reduction with ascorbate, while treatment with EGTA of the reduced, partially activated, form abolishes the activity. We conclude that the active enzyme is a mixed-valence form with the low-potential haem in a high-spin state that is stabilized by Ca2+. Dilution of the enzyme results in a progressive loss of activity, the extent of which depends on the degree of dilution. Most of the activity lost upon dilution can be recovered after reconcentration. The M(r) of the enzyme on molecular-exclusion chromatography is concentration-dependent, with a shift to lower values at lower concentrations. Values of M(r) obtained are intermediate between those of a monomer (39,565) and a dimer. We propose that the active form of the enzyme is a dimer which dissociates at high dilution to give inactive monomers. From the activity of the enzyme at different dilutions, a KD of 0.8 microM can be calculated for the monomerdimer equilibrium. The cytochrome c peroxidase oxidizes horse ferrocytochrome c with first-order kinetics, even at high ferrocytochrome c concentrations. The maximal catalytic-centre activity (‘turnover number’) under the assay conditions used is 62,000 min-1, with a half-saturating ferrocytochrome c concentration of 3.3 microM. The corresponding values for the Paracoccus cytochrome c-550 (presumed to be the physiological substrate) are 85,000 min-1 and 13 microM. However, in this case, the kinetics deviate from first-order progress curves at all ferrocytochrome c concentrations. Consideration of the periplasmic environment in Paracoccus denitrificans leads us to propose that the enzyme will be present as the fully active dimer supplied with saturating ferrocytochrome c-550.

scholarly journals Redox-linked spin-state changes in the di-haem cytochrome c-551 peroxidase from Pseudomonas aeruginosa

1985 ◽  
Vol 230 (1) ◽  
pp. 227-237 ◽  
Author(s):  
N Foote ◽  
J Peterson ◽  
P M Gadsby ◽  
C Greenwood ◽  
A J Thomson
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cytochrome C ◽  
High Spin ◽  
Spin State ◽  
High Potential ◽  
Reduced Form ◽  
Inactive Form ◽  
Temperature Spectra ◽  
State Changes ◽  
Haem Protein

Magnetic-c.d., e.p.r. and optical-absorption spectra are reported for the half-reduced form of Pseudomonas aeruginosa cytochrome c-551 peroxidase, a di-haem protein, and its fluoride derivative. Comparison of this enzyme species with oxidized peroxidase shows the occurrence of spin-state changes at both haem sites. The high-potential haem changes its state from partially high-spin to low-spin upon reduction. This is linked to a structural alteration at the ferric low-potential haem group, causing it to change from low-spin to high-spin. Low-temperature spectra demonstrate photolysis of an endogenous ligand of the high-potential haem. In addition, an inactive form of enzyme is examined in which the structural change at the ferric low-potential haem does not occur on reduction of the high-potential haem.

Theoretical study on the reduction reactions from solid char(N): The effect of the nearby group and the high-spin state

Energy ◽  
2019 ◽  
Vol 189 ◽  
pp. 116286 ◽  
Author(s):  
Hai Zhang ◽  
Lei Luo ◽  
Jiaxun Liu ◽  
Anyao Jiao ◽  
Jianguo Liu ◽  
...  
Keyword(s):  
High Spin ◽  
Spin State ◽  
Theoretical Study ◽  
High Spin State ◽  
Reduction Reactions

scholarly journals Supercooled high spin state in metallo-supramolecular assemblies

2007 ◽  
Vol 63 (a1) ◽  
pp. s202-s202
Author(s):  
U. Pietsch ◽  
M. Lommel ◽  
Y. Bodethin ◽  
D. Kurth ◽  
G. Schwarzl ◽  
...  
Keyword(s):  
High Spin ◽  
Spin State ◽  
High Spin State ◽  
Supramolecular Assemblies

High-Spin State Fe(III) Doped TiO2 for Electrocatalytic Nitrogen Fixation Induced by Surface F Modification

2021 ◽  
pp. 120809
Author(s):  
Guangxin Song ◽  
Rui Gao ◽  
Zhao Zhao ◽  
Yujun Zhang ◽  
Huaqiao Tan ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
High Spin ◽  
Spin State ◽  
High Spin State ◽  
Doped Tio2

Electric Field Induced Room Temperature Null to High Spin State Switching: A Computational Prediction

2019 ◽  
Vol 2 (4) ◽  
pp. 1900005 ◽  
Author(s):  
Carlos O. Amorim ◽  
João S. Amaral ◽  
João N. Gonçalves ◽  
Vítor S. Amaral
Keyword(s):  
Electric Field ◽  
High Spin ◽  
Spin State ◽  
Room Temperature ◽  
High Spin State ◽  
Computational Prediction ◽  
State Switching
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