Hydrogenases spill the beans: Key catalytic moves revealed

Hydrogenases catalyze the reversible splitting and production of hydrogen gas (H2), using complex catalytic cofactors comprising Earth-abundant nickel and/or iron ions. These enzymes, especially the [NiFe]-hydrogenases (fig. 1), are remarkably efficient, making them inspiring models for clean-energy technologies. Yet despite extensive study by many groups worldwide, key steps in their catalytic cycle have remained difficult to observe.