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Mössbauer effect and electron paramagnetic resonance studies on yeast aconitase
Journal of Biochemistry
|September 1, 1975
Summary
Yeast aconitase contains iron in a binuclear complex, similar to ferredoxins. Electron paramagnetic resonance (EPR) suggests small amounts of iron pairs contribute to its properties.
Area of Science:
- Biochemistry
- Biophysics
- Enzymology
Background:
- Aconitase (EC 4.2.1.3) is a crucial enzyme in the citric acid cycle.
- Understanding the iron-sulfur cluster in yeast aconitase is vital for its catalytic function.
Purpose of the Study:
- To characterize the iron-containing active site of yeast aconitase from Candida lipolytica.
- To investigate the oxidation states and magnetic coupling of iron ions within the enzyme.
Main Methods:
- Purification of yeast aconitase from Candida lipolytica.
- Mössbauer spectroscopy to analyze iron ions.
- Electron paramagnetic resonance (EPR) spectroscopy at various temperatures.
Main Results:
- Mössbauer spectra indicated two high-spin Fe(III) ions in an antiferromagnetically coupled binuclear cluster, resembling oxidized 2 Fe ferredoxins.
- A small amount of high-spin Fe(II) was also detected.
- EPR showed no signal at 77 K but a signal at 4.2 K, attributed to Fe(II)-Fe(III) pairs.
Conclusions:
- Yeast aconitase possesses an iron-sulfur cluster with structural and magnetic properties similar to ferredoxins.
- The observed EPR signal suggests the presence of mixed-valence iron pairs, potentially influencing enzyme activity.