121st General Meeting of the KCS

Type Oral Presentation
Area Oral Presentation of Young Inorganic Chemists
Room No. Samda Hall B
Time THU 10:20-:
Code INOR.O-5
Subject Synthetic Modeling of Mono-Iron Hydrogenase (Hmd): Utility of Anthracene Scaffold to Emulate the Facial Geometry of the Enzyme Active Site
Authors Junhyeok Seo
Department of Chemistry, Gwangju Institute of Science and Technology, Korea
Abstract Hydrogenases are metalloenzymes that involve energy metabolism in microbial communities as catalyzing the reversible oxidation of molecular hydrogen. The enzyme family is classified into three kinds, [FeFe]-, [NiFe]-, and [Fe]-hydrogenase. The dinuclear [FeFe], [NiFe]-hydrogenases have been studied in detail about their redox activity in the H2 generation and metabolism. Unlike the dinuclear hydrogenases, the third hydrogenase, mono-[Fe] hydrogenase, remains less studied. The enzyme catalyzes reversible conversion of methenyl-H4MPT+ to methylene-H4MPT during the methanogenic CO2 conversion as promoting the heterolytic splitting of H2. In aspect of the structure, the active site contains an Fe-ligating pyridone cofactor and another ligands of cysteine, two carbonyls and solvent in an octahedral geometry. The acyl-C, N donor in the pyridone ligand compose a facial coordination geometry together with the cysteine-S donor. We investigate the structural and functional relationship of the [Fe]-hydrogenase active site by synthesizing the model complexes. In recent progress, we realized the facial coordination geometry is a key to demonstrate the enzyme-like reactivity using synthetic model complexes. The C, N, S donors set in the facial geometry enforces a substrate binding site to place in trans to the Fe-C sigma donor. While the Lewis acidic Fe(II) center and the H4MPT+ split the molecular hydrogen, the acyl-C adjusts the Lewis acidity of Fe(II) ion to transfer hydride to H4MPT+ efficiently. In experimental comparisons with another model complex in a meridional coordination geometry, only the facial geometry model showed the enzyme-like reactivity, heterolytic splitting of H2 and the hydride transfer. We understand a reason of the facial geometry in the active site is to control the substrate (H2, methylene-H4MPT) interaction site to be placed in trans position to the Fe-acyl organometallic sigma bond. In the seminar, I will present a synthetic strategy using anthracene scaffold to construct our model complexes in the necessary facial coordination geometry, and additionally discuss the enzyme-like reactivities of the synthetic models towards molecular hydrogen and other substrates.
E-mail seojh@gist.ac.kr