Active-site structure, binding and redox activity of the heme-thiolate enzyme CYP2D6 immobilized on coated Ag electrodes: a surface-enhanced resonance Raman scattering study.
Surface-enhance resonance Raman scattering spectra of the heme-thiolate enzyme cytochrome P450 2D6 (CYP2D6) adsorbed on Ag electrodes coated with 11-mercaptoundecanoic acid (MUA) were obtained in various experimental conditions. An analysis of these spectra, and a comparison between them and the RR spectra of CYP2D6 in solution, indicated that the enzyme's active site retained its nature of six-coordinated low-spin heme upon immobilization. Moreover, the spectral changes detected in the presence of dextromethorphan (a CYP2D6 substrate) and imidazole (an exogenous heme axial ligand) indicated that the immobilized enzyme also preserved its ability to reversibly bind a substrate and form a heme-imidazole complex. The reversibility of these processes could be easily verified by flowing alternately solutions of the various compounds and the buffer through a home-built spectroelectrochemical flow cell which contained a sample of immobilized protein, without the need to disassemble the cell between consecutive spectral data acquisitions. Despite immobilized CYP2D6 being effectively reduced by a sodium dithionite solution, electrochemical reduction via the Ag electrode was not able to completely reduce the enzyme, and led to its extensive inactivation. This behavior indicated that although the enzyme's ability to exchange electrons is not altered by immobilization per se, MUA-coated electrodes are not suited to perform direct electrochemistry of CYP2D6.
Bonifacio
Alois
A
Analytical Chemistry and Applied Spectroscopy, Vrije Universiteit Amsterdam, De Boelelaan 1083a, 1081 HV Amsterdam, The Netherlands.
Millo
Diego
D
Keizers
Peter H J
PH
Boegschoten
Roald
R
Commandeur
Jan N M
JN
Vermeulen
Nico P E
NP
Gooijer
Cees
C
van der Zwan
Gert
G
D001665:Binding Sites; D002384:Catalysis; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000378:metabolism*; D006046:Gold / Q000737:chemistry*; D006418:Heme / Q000378:metabolism; D006801:Humans; D010084:Oxidation-Reduction; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013379:Substrate Specificity
D004800:Enzymes, Immobilized; D006418:Heme; D006046:Gold; D019389:Cytochrome P-450 CYP2D6