Concentration-Dependent Front Velocity of the Autocatalytic Hydrogenase Reaction
AUTOR(ES)
Bodó, Gabriella
FONTE
The Biophysical Society
RESUMO
HynSL hydrogenase from Thiocapsa roseopersicina was applied to catalyze the oxidation of molecular hydrogen in a new, improved, thin-layer reaction chamber. Investigation of the nature of this catalysis via the development of reduced benzyl viologen showed clearly the typical characteristics of an autocatalytic reaction: propagation of a reaction front originating from a single point, with a constant velocity of front propagation. The dependence of the reaction velocity on enzyme concentration was a power function with a positive enzyme concentration threshold, with an exponent of 0.4 ± 0.05. This indicates that the autocatalyst is an enzyme form. The front velocity decreased on increase of the electron acceptor concentration, as a sign that the autocatalyst interacts directly with the final electron acceptor. Overall, it may be concluded that the autocatalyst is an enzyme form in which [FeS]distal is reduced. Model calculations corroborate this. Because the reduction of all [FeS] clusters would be possible in a nonautocatalytic reaction, we hypothesize a small conformational change in the enzyme, catalyzed by the autocatalyst, which removes a block in the electron flow in either [NiFe] → [FeS]proximal or the [FeS]proximal → [FeS]distal reaction step, or removes a block of the penetration of gaseous hydrogen from the surface to the [NiFe] cluster.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2712045Documentos Relacionados
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