Molecular hydrogen is discussed as promising renewable energy source and attractive alternative to fossil fuels. Many microorganisms exploit the beneficial properties of hydrogen already since more than two billion years. They accommodate dedicated enzymes that either split or evolve molecular hydrogen according to the specific metabolic requirements of the cell.

These hydrogen-converting biocatalysts are called hydrogenases and occur in nature in different varieties. Most hydrogenases become inactivated or even destroyed in the presence of molecular oxygen. This intrinsic property represents a serious problem regarding biotechnological application. However, some hydrogenases maintain their catalytic activity in the presence of oxygen. Scientists from Humboldt University have already utilized this unusual characteristic for direct coupling of an oxygen-tolerant hydrogenase to the cyanobacterial photosynthesis apparatus in order to produce hydrogen in a light-dependent reaction.

A scientific team headed by Patrick Scheerer and Christian Spahn from Charité - Universitätsmedizin Berlin and Oliver Lenz and Bärbel Friedrich from Humboldt University now succeeded in solving the first X-ray crystal structure of a hydrogenase that produces hydrogen even at atmospheric oxygen concentration.

The X-ray crystal structure allows detailed insights into the three-dimensional architecture of the enzyme and its metal cofactors which participate in catalysis. The results have been published in Nature online (http://dx.doi.org/10.1038/nature10505). Interestingly, the hydrogenase contains a novel iron-sulfur center which acts as an electronic switch in the course of detoxification of detrimental oxygen. With this discovery, the scientists could substantiate the hypothesis that this particular group of hydrogenases is able to convert both, hydrogen and oxygen in a catalytic manner. During catalysis, oxygen becomes reduced to harmless water.

The new results are particularly relevant for fundamental research. Moreover, also the biotechnological application of hydrogenases, e.g. solar-driven hydrogen production by photosynthetic microorganisms and enzyme-driven biological fuel cells, may profit from the new findings. Furthermore, it is anticipated that the novel iron-sulfur center will inspire chemists to design model compounds with improved catalytic properties.

Published in: Fritsch, J., P. Scheerer, S. Frielingsdorf, S. Kroschinsky, B. Friedrich, O. Lenz & C. M. Spahn. The crystal structure of an oxygen-tolerant hydrogenase uncovers a novel iron-sulphur centre. Nature doi: 10.1038/nature10505 (2011)

http://dx.doi.org/10.1038/nature10505

FURTHER INFORMATION

Dr. Oliver Lenz
Institut für Biologie / Mikrobiologie der Humboldt-Universität zu Berlin
Telefon: 030 2093 8173
E-Mail: oliver.lenz@cms.hu-berlin.de

Patrick Scheerer
Institut für Medizinische Physik und Biophysik der Charité Berlin
Telefon: 030 450524178
E-Mail: patrick.scheerer@charite.de