Hydrogenase Spills Secret

An enzyme that taps into hydrogen’s power with minimal interference from oxygen possesses a novel iron-sulfur cluster, according to two crystallography studies (Nature, DOI: 10.1038/nature10505 and 10.1038/nature10504). With nickel and iron clusters, hydrogenase enzymes split H₂ into protons and electrons, but O₂ squelches the activity of most hydrogenases. Some hydrogenases work in air, however, and potential applications such as H₂-powered fuel cells or light-driven H₂ production from water depend on uncovering the secret to those enzymes’ success. A German team led by Oliver Lenz of Humboldt University and Christian M. T. Spahn of Charité University Hospital, both in Berlin, and a Japanese team led by the University of Hyogo’s Yoshiki Higuchi each detected a cluster never before seen in an enzyme—four iron atoms and three sulfurs. These clusters typically have four iron and four sulfur atoms. The researchers propose that the distinctive cluster converts invading O₂ to water by delivering electrons to the active site. Both studies showcase the versatility of iron-sulfur clusters, says Douglas C. Rees, who studies similar clusters at Caltech. “I would have loved to have done this work.”