The [FeFe]-hydrogenases are metalloenzymes that catalyze reversible activation of H2 by means of a unique catalytic site cofactor, the H-cluster. The rich structural diversity of this enzyme family provides a resource for establishing the principles required to design efficient catalysts that couple electrochemical potential, and proton/eelctron transfer to chemical bond formation. The goal of developing experimentally refined mechanistic models of [FeFe]-hydrogenases has been challenging due to inherently fast reaction kinetics (kcat ≥ 104 s-1) and difficulty in trapping short-lived intermediates. To address these challenges we have been investigating both native and variant forms of [FeFe]-hydrogenases by combination of biochemical, biophysical and spectroscopic approaches. Active site variants engineerd to have altered proton-transfer networks exhibit slower turnover, and have led to enrichment of species with unique spectral properties showing formation of a terminally bound metal hydride (Hhyd). This presentation will summarize progress on the study of the Hhyd intermediate of [FeFe]-hydrogenase, and will discuss the implication of how variantions to the protein environment control reactivity and reaction potentials as well as the mechanism of H2 activation in these enzymes.

Insights on the mechanism of H2 activation by [FeFe]-hydrogenases

254th National Meeting (2017)

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