Direct electrochemistry of Rhodococcus opacus hydrogenase for the catalysis of NAD + reduction

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 405; no. 1; pp. 189 - 195
• Main Authors: Gros, Pierre, Zaborosch, Christiane, Schlegel, Hans G., Bergel, Alain
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 12.04.1996; Elsevier Science; Elsevier
• Subjects: Catalysis; Chemical and Process Engineering; Chemistry; Electrochemistry; Engineering Sciences; Exact sciences and technology; General and physical chemistry; Kinetics and mechanism of reactions; NAD + electrochemical reduction; Rhodococcus opacus hydrogenase; NAD + electrochemical reduction; Rhodococcus opacus hydrogenase; Catalysis; Phosphates; Enzyme; Rhodococcus; Transition metal; Experimental study; Buffer solution; Electrodes; Hydrogenase; NAD; Chemical reduction; Electrocatalysis; Absorption spectrometry; Platinum; Bacteria; Actinomycetes; Oxidoreductases; Electrochemical reaction; Enzymatic reaction
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/0022-0728(95)04419-1

The catalysis of NAD + reduction by Rhodococcus opacus hydrogenase was investigated by spectroelectrochemistry in a thin layer cell on a platinum electrode. The NADH formation rates were significantly higher than those obtained with the hydrogenase of Alcaligenes eutrophus which has previously been identified as a good catalyst of this electrochemical reduction. As a consequence, for the first time to our knowledge, a well-identified current peak which corresponded to NAD + reduction was observed on the voltammograms obtained with a platinum cathode. Thanks to the efficiency of this catalysis, it has been possible to improve the understanding of the mechanism. A two-step mechanism was assumed, according to the structure of the hydrogenase which is composed of two dimers with distinct hydrogenase and diaphorase activity. At high potentials (above −0.66 V (SCE)) only the diaphorase dimer was reduced by direct electron transfer from the electrode, without intervention of any hydrogen intermediate. For more negative potentials, a reduced hydrogen species adsorbed on the electrode surface was involved in the mechanism. In this case, catalysis followed a more classic catalytic pathway via the hydrogenase dimer and an intramolecular electron transfer to the diaphorase dimer, which reduced NAD +.