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Fe-S centers in lactyl-CoA dehydratase
Biochemistry
|November 18, 1986
Summary
Lactyl-CoA dehydratase enzyme E2 contains iron-sulfur clusters, with distinct EPR signals suggesting a [4Fe-4S] and a [3Fe-3/4S] cluster. These signals change upon reduction and substrate addition.
Area of Science:
- Biochemistry
- Enzymology
- Bioinorganic Chemistry
Background:
- Lactyl-CoA dehydratase is a crucial enzyme requiring ATP and composed of subunits E1 and E2.
- Enzyme E2 is characterized by a high iron content, suggesting the presence of iron-sulfur clusters.
Purpose of the Study:
- To investigate the structure and properties of iron-sulfur clusters within lactyl-CoA dehydratase E2.
- To characterize the electron paramagnetic resonance (EPR) signals of E2 and their relationship to iron content.
Main Methods:
- Electron Paramagnetic Resonance (EPR) spectroscopy at low temperatures (4 K).
- Quantification of iron and inorganic sulfur content in enzyme E2.
- Computer simulation using S = 1/2 spin Hamiltonian for EPR spectral analysis.
- Enzyme activity assays and substrate binding studies.
Main Results:
- Enzyme E2 contains approximately 8 Fe atoms and 7 inorganic sulfur atoms per molecule, indicating Fe-S cluster formation.
- Two distinct EPR signals were observed in E2 at low temperatures, with specific g-values and symmetries.
- Signal intensity decreased upon reduction with Na2S2O4, and signal 2 was significantly altered by acrylyl-CoA or lactyl-CoA.
- Proposed identification of signal 1 as a [4Fe-4S] cluster and signal 2 as a [3Fe-3/4S] cluster.
Conclusions:
- Lactyl-CoA dehydratase E2 harbors at least two distinct iron-sulfur clusters with unique spectroscopic properties.
- The observed EPR signals are attributed to specific [4Fe-4S] and [3Fe-3/4S] clusters.
- Substrate binding influences the iron-sulfur cluster environment, particularly the [3Fe-3/4S] cluster.