TY  - JOUR
A1  - Duffus, Benjamin R.
A1  - Schrapers, Peer
A1  - Schuth, Nils
A1  - Mebs, Stefan
A1  - Dau, Holger
A1  - Leimkühler, Silke
A1  - Haumann, Michael
T1  - Anion binding and oxidative modification at the molybdenum cofactor of formate dehydrogenase from Rhodobacter capsulatus studied by X-ray absorption spectroscopy
JF  - Inorganic chemistry
N2  - Formate dehydrogenase (FDH) enzymes are versatile catalysts for CO2 conversion. The FDH from Rhodobacter capsulatus contains a molybdenum cofactor with the dithiolene functions of two pyranopterin guanine dinucleotide molecules, a conserved cysteine, and a sulfido group bound at Mo(VI). In this study, we focused on metal oxidation state and coordination changes in response to exposure to O-2, inhibitory anions, and redox agents using X-ray absorption spectroscopy (XAS) at the Mo K-edge. Differences in the oxidative modification of the bis-molybdopterin guanine dinucleotide (bis-MGD) cofactor relative to samples prepared aerobically without inhibitor, such as variations in the relative numbers of sulfido (Mo=S) and oxo (Mo=O) bonds, were observed in the presence of azide (N-3(-)) or cyanate (OCN-). Azide provided best protection against O-2, resulting in a quantitatively sulfurated cofactor with a displaced cysteine ligand and optimized formate oxidation activity. Replacement of the cysteine ligand by a formate (HCO2-) ligand at the molybdenum in active enzyme is compatible with our XAS data. Cyanide (CN-) inactivated the enzyme by replacing the sulfido ligand at Mo(VI) with an oxo ligand. Evidence that the sulfido group may become protonated upon molybdenum reduction was obtained. Our results emphasize the role of coordination flexibility at the molybdenum center during inhibitory and catalytic processes of FDH enzymes.
Y1  - 2020
U6  - https://doi.org/10.1021/acs.inorgchem.9b01613
SN  - 0020-1669
SN  - 1520-510X
VL  - 59
IS  - 1
SP  - 214
EP  - 225
PB  - American Chemical Society
CY  - Washington, DC
ER  -