A mechanistic and electrochemical study of the interaction between dimethyl sulfide dehydrogenase and its electron transfer partner cytochrome c2
Author(s)
L. Creevey, Nicole
G. McEwan, Alastair
V. Bernhardt, Paul
Griffith University Author(s)
Year published
2008
Metadata
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Dimethyl sulfide dehydrogenase isolated from the photosynthetic bacterium Rhodovulum sulfidophilum is a heterotrimeric enzyme containing a molybdenum cofactor at its catalytic site, as well as five iron-sulfur clusters and a heme b cofactor. It oxidizes dimethyl sulfide (DMS) to dimethyl sulfoxide in its native role and transfers electrons to the photochemical reaction center. There is genetic evidence that cytochrome c 2 mediates this process, and the steady state kinetics experiments reported here demonstrated that cytochrome c 2 accepts electrons from DMS dehydrogenase. At saturating concentrations of both substrate (DMS) ...
View more >Dimethyl sulfide dehydrogenase isolated from the photosynthetic bacterium Rhodovulum sulfidophilum is a heterotrimeric enzyme containing a molybdenum cofactor at its catalytic site, as well as five iron-sulfur clusters and a heme b cofactor. It oxidizes dimethyl sulfide (DMS) to dimethyl sulfoxide in its native role and transfers electrons to the photochemical reaction center. There is genetic evidence that cytochrome c 2 mediates this process, and the steady state kinetics experiments reported here demonstrated that cytochrome c 2 accepts electrons from DMS dehydrogenase. At saturating concentrations of both substrate (DMS) and cosubstrate (cytochrome c 2), Michaelis constants, K M,DMS and K M,cyt of 53 and 21 卬 respectively, were determined at pH 8. Further kinetic analysis revealed a "ping-pong" enzyme reaction mechanism for DMS dehydrogenase with its two reactants. Direct cyclic voltammetry of cytochrome c 2 immobilized within a polymer film cast on a glassy carbon electrode revealed a reversible FeIII/II couple at +328 mV versus the normal hydrogen electrode at pH 8. The FeIII/II redox potential exhibited only minor pH dependence. In the presence of DMS dehydrogenase and DMS, the peak-shaped voltammogram of cytochrome c 2 is transformed into a sigmoidal curve consistent with a steady-state (catalytic) reaction. The cytochrome c 2 effectively mediates electron transfer between the electrode and DMS dehydrogenase during turnover and a significantly lower apparent electrochemical Michaelis constant of13(ᱩ 占was obtained. The pH optimum for catalytic DMS oxidation by DMS dehydrogenase with cytochrome c 2 as the electron acceptor was found to be approximately 8.3.
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View more >Dimethyl sulfide dehydrogenase isolated from the photosynthetic bacterium Rhodovulum sulfidophilum is a heterotrimeric enzyme containing a molybdenum cofactor at its catalytic site, as well as five iron-sulfur clusters and a heme b cofactor. It oxidizes dimethyl sulfide (DMS) to dimethyl sulfoxide in its native role and transfers electrons to the photochemical reaction center. There is genetic evidence that cytochrome c 2 mediates this process, and the steady state kinetics experiments reported here demonstrated that cytochrome c 2 accepts electrons from DMS dehydrogenase. At saturating concentrations of both substrate (DMS) and cosubstrate (cytochrome c 2), Michaelis constants, K M,DMS and K M,cyt of 53 and 21 卬 respectively, were determined at pH 8. Further kinetic analysis revealed a "ping-pong" enzyme reaction mechanism for DMS dehydrogenase with its two reactants. Direct cyclic voltammetry of cytochrome c 2 immobilized within a polymer film cast on a glassy carbon electrode revealed a reversible FeIII/II couple at +328 mV versus the normal hydrogen electrode at pH 8. The FeIII/II redox potential exhibited only minor pH dependence. In the presence of DMS dehydrogenase and DMS, the peak-shaped voltammogram of cytochrome c 2 is transformed into a sigmoidal curve consistent with a steady-state (catalytic) reaction. The cytochrome c 2 effectively mediates electron transfer between the electrode and DMS dehydrogenase during turnover and a significantly lower apparent electrochemical Michaelis constant of13(ᱩ 占was obtained. The pH optimum for catalytic DMS oxidation by DMS dehydrogenase with cytochrome c 2 as the electron acceptor was found to be approximately 8.3.
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Journal Title
Journal of Biological Inorganic Chemistry
Volume
13
Issue
3
Subject
Chemical Sciences not elsewhere classified
Inorganic Chemistry
Medicinal and Biomolecular Chemistry
Biochemistry and Cell Biology