TY - JOUR
T1 - Electrochemical study on cytochrome c peroxidase from Paracoccus denitrificans: A shifting pattern of structural and thermodynamic properties as the enzyme is activated
AU - Lopes, Helder
AU - Pettigrew, Graham W.
AU - Moura, Isabel
AU - Moura, José J. G.
N1 - This work was supported by STRIDE C/ CEN/538/2, Welcome Trust, British Council, JNICT and PRAXIS 2/2.1/QUI/312/94.
PY - 1998/12/1
Y1 - 1998/12/1
N2 - The di-haem cytochrome c peroxidase of Paracoccus denitrificans is a calcium binding dimer of 37.5 kDa subunits. It is responsible for reduction of H2O2 to H2O with oxidation of cytochrome c550 and is isolated in a fully oxidised state (inactive) in which one haem (centre I) is in a high- spin/low-spin equilibrium and high potential and the other (centre II) is low-spin and low potential. The enzyme undergoes direct electron transfer (without the need for mediators) with a 4,4'-dithiodipyridine-modified gold electrode and the response of both haem groups can be observed. By combination of the cyclic and pulse voltammetric data with the established spectroscopic information, it was demonstrated that entry of one electron to the high potential haem leads (in a mechanism involving strong haem-haem interactions) to a complex change of spin states and redox potentials of both haems in order to attain a 'ready state' for binding, reduction and cleavage of the hydrogen peroxide. In the absence of endogenous calcium, haem communication can be completely disconnected and is recovered only when Ca2+ is added, an essential step for the formation of the peroxidatic site. The intricate electrochemical behaviour of this enzyme was interpreted as a mechanism involving, both reduction and oxidation of the high potential haem, an interfacial electron transfer coupled to a homogenous chemical reaction (EC mechanism). We discuss two different models for the sequence of events leading to the appearance of the active pentacoordinated peroxidatic haem.
AB - The di-haem cytochrome c peroxidase of Paracoccus denitrificans is a calcium binding dimer of 37.5 kDa subunits. It is responsible for reduction of H2O2 to H2O with oxidation of cytochrome c550 and is isolated in a fully oxidised state (inactive) in which one haem (centre I) is in a high- spin/low-spin equilibrium and high potential and the other (centre II) is low-spin and low potential. The enzyme undergoes direct electron transfer (without the need for mediators) with a 4,4'-dithiodipyridine-modified gold electrode and the response of both haem groups can be observed. By combination of the cyclic and pulse voltammetric data with the established spectroscopic information, it was demonstrated that entry of one electron to the high potential haem leads (in a mechanism involving strong haem-haem interactions) to a complex change of spin states and redox potentials of both haems in order to attain a 'ready state' for binding, reduction and cleavage of the hydrogen peroxide. In the absence of endogenous calcium, haem communication can be completely disconnected and is recovered only when Ca2+ is added, an essential step for the formation of the peroxidatic site. The intricate electrochemical behaviour of this enzyme was interpreted as a mechanism involving, both reduction and oxidation of the high potential haem, an interfacial electron transfer coupled to a homogenous chemical reaction (EC mechanism). We discuss two different models for the sequence of events leading to the appearance of the active pentacoordinated peroxidatic haem.
KW - Cytochrome c peroxidase
KW - Electrochemistry
KW - Spin and redox changes
UR - http://www.scopus.com/inward/record.url?scp=0031774177&partnerID=8YFLogxK
U2 - 10.1007/s007750050277
DO - 10.1007/s007750050277
M3 - Article
AN - SCOPUS:0031774177
SN - 0949-8257
VL - 3
SP - 632
EP - 642
JO - JBIC Journal of Biological Inorganic Chemistry
JF - JBIC Journal of Biological Inorganic Chemistry
IS - 6
ER -