Open AccessDirect Electrochemistry of Megasphaera Elsdenii Iron Hydrogenase
Author(s) -
Butt Julea N.,
Filipiak Marian,
Hagen Wilfred R.
Publication year - 1997
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1997.00116.x
Subject(s) - hydrogenase , catalysis , chemistry , electrochemistry , cyclic voltammetry , iron–sulfur cluster , inorganic chemistry , glassy carbon , enzyme , electrode , organic chemistry
The Fe‐hydrogenase from Megasphaera elsdenii undergoes direct electron exchange with glassy carbon electrodes. Cyclic voltammetry defines the catalytic performance of the enzyme over a continuous but precisely defined range of potentials. In the presence of H 2 and protons the bias of the enzyme towards H 2 production is readily visualised. Variation of the response with pH indicates that protein ionisations with pK of approximately 6.7 and 8.3 regulate the catalytic activity. Possible origins for these observations in the chemistry of the H 2 ‐activating site are discussed. The mid‐wave potential of the catalytic response, E mid , is defined as the catalytic operating potential of the enzyme. Under an atmosphere of hydrogen E mid , =−421 ± 10 mV, pH 7 with a variation of −21 ± 4 mV pH −1 , 22°C. Deviation of E mid from the thermodynamic potential of the hydrogen/proton couple reflects the enzyme's influence over the catalysed reaction. E mid is the reduction potential of the H 2 ‐activating centre (H‐cluster) in the absence of kinetic bottle‐necks at other steps in the reaction mechanism.