Structural foundations for the O2 resistance of Desulfomicrobium baculatum [NiFeSe]-hydrogenase.

This study shows how the NiFeSe site of an anaerobically purified O2-resistant hydrogenase reacts with air to give a seleninate as the first product. Less oxidized states of the active site are readily reduced in the presence of X-rays. Reductive enzyme activation requires an efficient pathway for water escape.