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Model for acetylene reduction by nitrogenase derived from density functional theory
Johannes Kästner1, Peter E Blöchl
1Institute for Theoretical Physics, Clausthal University of Technology, D-38678 Clausthal-Zellerfeld, Germany.
Inorganic Chemistry
|June 21, 2005
Summary
This study reveals how acetylene reduction occurs at the iron-molybdenum (FeMo) cofactor of nitrogenase. Acetylene binds to a less reduced cofactor state, explaining observed inhibition patterns and hydrogen suppression during nitrogen fixation.
Area of Science:
- Biochemistry
- Computational Chemistry
- Enzymology
Background:
- Nitrogenase is a crucial enzyme catalyzing nitrogen fixation.
- Understanding the mechanism of acetylene reduction by nitrogenase provides insights into nitrogen fixation.
Purpose of the Study:
- To investigate the catalytic cycle of acetylene reduction at the FeMo cofactor of nitrogenase.
- To elucidate the binding mechanism of acetylene and its interaction with the cofactor.
Main Methods:
- Density functional theory (DFT) calculations were employed.
- A computational model of the FeMo cofactor was developed.
Main Results:
- Acetylene (C2H2) binds to the same site as nitrogen (N2) but at a less reduced cofactor state.
- Sulfur bridges in the cofactor open during acetylene binding, similar to N2 binding.
- The model explains noncompetitive inhibition of N2 reduction by C2H2 and competitive inhibition of C2H2 reduction by N2.
Conclusions:
- The proposed mechanism is consistent with experimental stereoselectivity.
- Acetylene's ability to suppress H2 production by nitrogenase is explained by this mechanism.