tailieunhanh - Báo cáo khóa học: Direct electrochemistry of the Desulfovibrio gigas aldehyde oxidoreductase

This work reports on the direct electrochemistry of the Desulfovibrio gigasaldehyde oxidoreductase (DgAOR), a molybdenum enzyme of the xanthine oxidase family that contains three redox-active cofactors: two [2Fe-2S] centers and a molybdopterin cytosine dinucleotide cofactor. The voltammetric behavior of the enzyme was analyzed at gold and carbon (pyrolytic graphite and glassy carbon) elec-trodes. Two different strategies were used: one with the molecules confined to the electrode surface and a second withDgAOR in solution | Eur. J. Biochem. 271 1329-1338 2004 FEBS 2004 doi Direct electrochemistry of the Desulfovibrio gigas aldehyde oxidoreductase Margarida M. Correia dos Santos1 Patricia M. P. Sousa1 M. Lurdes S. Goncalves1 M. Joao Romao2 Isabel Moura2 and Jose J. G. Moura2 1Centro de Quimica Estrutural Instituto Superior Tecnico Lisboa Portugal 2REQUIMTE Departamento de Quimica Centro de Qulmica Fina e Biotecnologica Faculade de Ciencias e Tecnologia Universidade Nova de Lisboa Portugal This work reports on the direct electrochemistry of the Desulfovibrio gigas aldehyde oxidoreductase DgAOR a molybdenum enzyme of the xanthine oxidase family that contains three redox-active cofactors two 2Fe-2S centers and a molybdopterin cytosine dinucleotide cofactor. The voltammetric behavior of the enzyme was analyzed at gold and carbon pyrolytic graphite and glassy carbon electrodes. Two different strategies were used one with the molecules confined to the electrode surface and a second with DgAOR in solution. In all of the cases studied electron transfer took place although different redox reactions were responsible for the voltammetric signal. From a thorough analysis of the voltammetric responses and the structural properties of the molecular surface of DgAOR the redox reaction at the carbon electrodes could be assigned to the reduction of the more exposed iron cluster 2Fe-2S II whereas reduction of the molybdopterin cofactor occurs at the gold electrode. Voltammetric results in the presence of aldehydes are also reported and discussed. Keywords aldehyde oxidoreductase Desulfovibrio gigas electrochemistry. Voltammetric techniques are useful for unraveling important aspects of the chemistry of metalloproteins and metal-loenzymes 1-4 . Unlike the more conventional and widely used potentiometric titrations voltammetric methods allow in situ measurement of reduction potentials together with acquisition of information about the kinetics of the electrode reactions .