REDOX THERMODYNAMICS 17

A010 ELECTRON TRANSFER BETWEEN [NiFe] HYDROGENASES AND

SMALL ELECTRON CARRIERS FROM SULFATE REDUCERS

Ricardo m1 ‘Cristina Moreno’, Isabel Mowal s2v3, Jean LeGall

and Josli. G. Mburalf

1 Depattamento de Quimica, FCT, Universidade Nova de Lisboa, 2825 Monte de Caparica, Portugal

* Centro de Tecnologia Quimica e Bioldgica, Aptartado127, 2780 Oeiras, Portugal 3 Department of Biochemistry, UGA, Athens, GA 30802, USA

The electron transfer process occuring between [NiFe] hydrogenases and several

electron transfer proteins from Desulfovibfio sp. was investigated by

electrochemical methods (cyclic voltammetry, square wave voltammetry and

chronoamperometry). These studies were also supported by optical spectroscopy.

The small electron carriers studied are cytochrome q, [3Fe-4S] and [4Fe-4S]

ferredoxins and rubredoxin. The second order fate constants k for the reaction

between the reduced small electron carriers and hydrogenases were calculated

based on the theory of the simplest electrocatalytic mechanism [l]. Under these

experimental conditions, hydrogen evolution is monitored by mass spectrometry.

Work supported by INK?, JNICT, STRIDE, GBF and NATO (Science t?x Stabiity).

[l] Moreno, C., Costa, C., Moura, I., LeGall, J., tiu, M.Y., Payne, W.J., Dijk, C. van

and Moura, J.J.G. (1993) Eur.J.Biochem. 212 79-86.