2025/05/13 by Effie C. Kisgeropoulos, Michael W. Ratzloff, Ekaterina M. Stroeva-Dahl +6 · 1 voice · 2 citations
Energy · Engineering · #Advanced battery technologies research #Electrocatalysts for Energy Conversion #Metalloenzymes and iron-sulfur proteins
paper · pdf · doi:10.1021/acs.biochem.5c00066
openalex publication_date 2025/05/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/22
High Resolution Image Download MS PowerPoint Slide [FeFe]-Hydrogenases are structurally diverse enzymes that catalyze reversible H 2 activation at a catalytic cofactor or H-cluster. The H-cluster is a [4Fe-4S] cubane linked by a cysteine thiolate to a diiron subsite containing unique CO, CN -, and dithiomethylamine ligands. The established H-cluster resting state of [4Fe-4S] 2+ -[Fe II -Fe I ], or H ox, functions in H 2 binding and oxidation, or by proton-coupled reduction initiates H 2 evolution. In contrast, in Clostridium pasteurianum [FeFe]-hydrogenase III (CpIII) the resting state of the H-cluster is fully oxidized, [4Fe-4S] 2+ -[Fe II -Fe II ], or H ox+1 . To begin to understand if H ox+1 has a role in the mechanism of CpIII, we determined the spectroscopic and redox properties of CpIII H-cluster states under catalytic conditions. CpIII poised in H ox+1 and either equilibrated under 1 atm of H 2 or reduced with sodium dithionite, resulted in a mixture of reduced states including H ox ( E m 8 = −407 mV), H trans -like [4Fe-4S] + -[Fe II -Fe II ] ( E m 8 = −418 mV), H red [4Fe-4S] + -[Fe II -Fe I ], and H redH+ [4Fe-4S] 2+ -[Fe I -Fe I ] ( E m 8 = −455–480 mV). Under H 2 the population of the H trans -like state was >20-fold higher than H ox, implicating a role in CpIII catalysis. Unlike other enzymes, there was no spectral evidence of fully reduced states, such as H sredH+ ([4Fe-4S] + -[Fe I -Fe I ]) or H hyd ([4Fe-4S] + -[Fe II- Fe II ]-H – ). Thus, while the H-cluster states of CpIII encompass most of the catalytic intermediates, it is either unable to form H sredH+ and H hyd, or these states are highly destabilized in CpIII. Thus, these results demonstrate that catalytic intermediates of reduced CpIII differ from the typical intermediates of other catalytic [FeFe]-hydrogenases and may explain the catalytic preference for H 2 production.