IR spectroelectrochemical study of the binding of carbon monoxide to the active site of Desulfovibrio fructosovorans Ni-Fe hydrogenase.
The binding of carbon monoxide, a competitive inhibitor of many hydrogenases, to the active site of Desulfovibrio fructosovorans hydrogenase has been studied by infrared spectroscopy in a spectroelectrochemical cell. Direct evidence has been obtained of which redox states of the enzyme can bind extrinsic CO. Redox states A, B and SU do not bind extrinsic CO; only after reductive activation of the hydrogenase can CO bind to the active site. Two states with bound extrinsic CO can be distinguished by FTIR. These two states are in redox equilibrium and are most probably due to different oxidation states of the proximal 4Fe-4S cluster. Vibrational frequencies and theoretical quantum mechanics studies (DFT) of this process preclude the possibility of strong bonding of extrinsic CO to the Fe or Ni atoms of the active site. We propose that CO inhibition is caused by weak interaction of the extrinsic ligand with the Ni atom, blocking electron and proton transfer at the active site. A calculated structure with a weakly bound extrinsic CO at Ni has relative CO frequencies in excellent agreement with the experimental ones.
De Lacey
Antonio L
AL
Instituto de Catalisis, CSIC, Campus Universidad Autonoma-Cantoblanco, Madrid 28049, Spain. alopez@icp.csic.es
Stadler
Christian
C
Fernandez
Victor M
VM
Hatchikian
E Claude
EC
Fan
Hua-Jun
HJ
Li
Shuhua
S
Hall
Michael B
MB
D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain; D003901:Desulfovibrio / Q000201:enzymology*; D004563:Electrochemistry; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding; D013055:Spectrophotometry, Infrared / Q000379:methods*; D017186:Titrimetry
D002248:Carbon Monoxide; C043296:nickel-iron hydrogenase; D006864:Hydrogenase