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Chlorite dismutase from Ideonella dechloratans
K Stenklo1, H D Thorell, H Bergius
1Department of Chemistry, Karlstad University, Sweden.
Summary
Chlorite dismutase was purified from Ideonella dechloratans, revealing unique catalytic properties and heme reduction distinct from other bacterial enzymes. This study characterizes the enzyme
Area of Science:
- Biochemistry
- Microbiology
- Enzymology
Background:
- Chlorite dismutase enzymes are crucial for chlorate metabolism in bacteria.
- Previous research identified a similar enzyme in bacterium GR-1, but with differing properties.
Purpose of the Study:
- To purify and characterize chlorite dismutase from Ideonella dechloratans.
- To compare its properties with the known GR-1 enzyme.
- To investigate the enzyme's heme group characteristics and N-terminal sequence.
Main Methods:
- Enzyme purification techniques.
- Spectroscopic analysis (optical and EPR).
- Redox titration.
- N-terminal amino acid sequencing.
Main Results:
- Purified Ideonella chlorite dismutase is a tetramer with a subunit molecular mass of 25,000 Da and 0.6 heme/subunit.
- The enzyme's heme group is readily reduced by dithionite and has a midpoint potential of -21 mV at pH 7.
- Spectroscopic analysis revealed high-spin ferric heme at neutral pH, transitioning to a low-spin form in alkaline conditions.
- The 22-residue N-terminal sequence showed no homology in existing databases.
Conclusions:
- Ideonella dechloratans chlorite dismutase exhibits distinct catalytic and heme reduction properties compared to the GR-1 enzyme.
- The enzyme's heme group undergoes pH-dependent spin state changes.
- The unique N-terminal sequence suggests a novel enzyme family.
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