ja510169s_si_001.pdf (1.12 MB)
[FeFe]-Hydrogenase Oxygen Inactivation Is Initiated at the H Cluster 2Fe Subcluster
journal contribution
posted on 2015-02-11, 00:00 authored by Kevin
D. Swanson, Michael W. Ratzloff, David W. Mulder, Jacob H. Artz, Shourjo Ghose, Andrew Hoffman, Spencer White, Oleg A. Zadvornyy, Joan B. Broderick, Brian Bothner, Paul W. King, John W. PetersThe [FeFe]-hydrogenase catalytic
site H cluster is a complex iron
sulfur cofactor that is sensitive to oxygen (O2). The O2 sensitivity is a significant barrier for production of hydrogen
as an energy source in water-splitting, oxygenic systems. Oxygen reacts
directly with the H cluster, which results in rapid enzyme inactivation
and eventual degradation. To investigate the progression of O2-dependent [FeFe]-hydrogenase inactivation and the process
of H cluster degradation, the highly O2-sensitive [FeFe]-hydrogenase
HydA1 from the green algae Chlamydomonas reinhardtii was exposed to defined concentrations of O2 while monitoring
the loss of activity and accompanying changes in H cluster spectroscopic
properties. The results indicate that H cluster degradation proceeds
through a series of reactions, the extent of which depend on the initial
enzyme reduction/oxidation state. The degradation process begins with
O2 interacting and reacting with the 2Fe subcluster, leading
to degradation of the 2Fe subcluster and leaving an inactive [4Fe-4S]
subcluster state. This final inactive degradation product could be
reactivated in vitro by incubation with 2Fe subcluster
maturation machinery, specifically HydFEG, which was observed
by recovery of enzyme activity.