EPR characterization of the molybdenum(V) forms of formate dehydrogenase from Desulfovibrio desulfuricans ATCC 27774 upon formate reduction,
Rivas, M. G., Gonzalez P. J., Brondino C. D., Moura J. J., and Moura I.
, J Inorg Biochem, Nov, Volume 101, Number 11-12, p.1617-22, (2007)
AbstractThe EPR characterization of the molybdenum(V) forms obtained on formate reduction of both as-prepared and inhibited formate dehydrogenase from Desulfovibrio desulfuricans ATCC 27774, an enzyme that catalyzes the oxidation of formate to CO(2), is reported. The Mo(V) EPR signal of the as-prepared formate-reduced enzyme is rhombic (g(max)=2.012, g(mid)=1.996, g(min)=1.985) and shows hyperfine coupling with two nuclear species with I=1/2. One of them gives an anisotropic splitting and is not solvent exchangeable (A(max)=11.7, A(mid)=A(min)=non-detectable, A-values in cm(-1)x10(-4)). The second species is exchangeable with solvent and produces a splitting at the three principal g-values (A(max)=7.7, A(mid)=10.0, A(min)=9.3). The hyperfine couplings of the non-solvent and solvent exchangeable nuclei are assigned to the hydrogen atoms of the beta-methylene carbon of a selenocysteine and to a Mo ligand whose nature, sulfydryl or hydroxyl, is still in debate. The Mo(V) species obtained in the presence of inhibitors (azide or cyanide) yields a nearly axial EPR signal showing only one detectable splitting given by nuclear species with I=1/2 (g(max)=2.092, g(mid)=2.000, g(min)=1.989, A(max)=non-detectable, A(mid)=A(min)=7.0), which is originated from the alpha-proton donated by the formate to a proximal ligand of the molybdenum. The possible structures of both paramagnetic molybdenum species (observed upon formate reduction in presence and absence of inhibitors) are discussed in comparison with the available structural information of this enzyme and the structural and EPR properties of the closely related formate dehydrogenase-H from Escherichia coli.
EPR spectroscopy on mononuclear molybdenum-containing enzymes,
Maia, L. B., Moura I., and Moura J. J. G.
, Future Directions in Metalloprotein and Metalloenzyme Research, Biological Magnetic Resonance, Vol. 33 (ISBN: 978-3-319-59100-1), Cham, p.55-101, (2017)
AbstractThe biological relevance of molybdenum was demonstrated in the early 1950s-1960s, by Bray, Beinert, Lowe, Massey, Palmer, Ehrenberg, Pettersson, Vänngård, Hanson and others, with ground-breaking studies performed, precisely, by electron paramagnetic resonance (EPR) spectroscopy. Those earlier studies, aimed to investigate the mammalian xanthine oxidase and avian sulfite oxidase enzymes, demonstrated the surprising biological reduction of molybdenum to the paramagnetic Mo5+. Since then, EPR spectroscopy, alongside with other spectroscopic methods and X-ray crystallography, has contributed to our present detailed knowledge about the active site structures, catalytic mechanisms and structure/activity relationships of the molybdenum-containing enzymes.
This Chapter will provide a perspective on the contribution that EPR spectroscopy has made to some selected systems. After a brief overview on molybdoenzymes, the Chapter will be focused on the EPR studies of mammalian xanthine oxidase, with a brief account on the prokaryotic aldehyde oxidoreductase, nicotinate dehydrogenase and carbon monoxide dehydrogenase, vertebrate sulfite oxidase, and prokaryotic formate dehydrogenases and nitrate reductases.
EPR studies of the Mo-enzyme aldehyde oxidoreductase from Desulfovibrio gigas: an application of the Bloch-Wangsness-Redfield theory to a system containing weakly-coupled paramagnetic redox centers with different relaxation rates,
Gonzalez, P. J., Barrera G. I., Rizzi A. C., Moura J. J., Passeggi M. C., and Brondino C. D.
, J Inorg Biochem, Oct, Volume 103, Number 10, p.1342-6, (2009)
AbstractElectron transfer proteins and redox enzymes containing paramagnetic redox centers with different relaxation rates are widespread in nature. Despite both the long distances and chemical paths connecting these centers, they can present weak magnetic couplings produced by spin-spin interactions such as dipolar and isotropic exchange. We present here a theoretical model based on the Bloch-Wangsness-Redfield theory to analyze the dependence with temperature of EPR spectra of interacting pairs of spin 1/2 centers having different relaxation rates, as is the case of the molybdenum-containing enzyme aldehyde oxidoreductase from Desulfovibrio gigas. We analyze the changes of the EPR spectra of the slow relaxing center (Mo(V)) induced by the faster relaxing center (FeS center). At high temperatures, when the relaxation time T(1) of the fast relaxing center is very short, the magnetic coupling between centers is averaged to zero. Conversely, at low temperatures when T(1) is longer, no modulation of the coupling between metal centers can be detected.
Evaluation of Sweat Sampling Procedures for Human Stress Biomarkers Detection,
Nunes, M. J., Moura J. J. G., Noronha J. P., Branco L. C., Samhan-Arias A., Sousa J. P., Rouco C., and Cordas C.
, Analytica, Volume 3, p.178–194, (2022)