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S-adenosylmethionine radical enzymes.
E Neil G Marsh1, Anjali Patwardhan, Marja S Huhta
1Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA. nmarsh@umich.edu
Bioorganic Chemistry
|September 24, 2004
Summary
S-adenosylmethionine (SAM) radical enzymes are widespread catalysts. Recent studies reveal their mechanisms and structures, including iron-sulfur clusters and X-ray crystallography of key enzymes.
Area of Science:
- Biochemistry
- Enzymology
- Organic Chemistry
Background:
- S-adenosylmethionine (SAM) is a known precursor to organic radicals.
- These radicals are generated via one-electron reduction and subsequent cleavage of SAM.
- The widespread nature and diverse catalytic roles of SAM radical enzymes are recently recognized.
Purpose of the Study:
- To investigate the mechanisms of SAM radical enzymes.
- To understand the role of iron-sulfur clusters in SAM reduction.
- To elucidate the structural basis of SAM radical enzyme function.
Main Methods:
- Spectroscopic investigations
- Kinetic studies
- X-ray crystallography
Main Results:
- Identification of several new SAM radical enzymes.
- Uncovering the mechanism of SAM reduction by iron-sulfur clusters.
- Solving the first X-ray structures of coproporphyrinogen-III oxidase and biotin synthase.
Conclusions:
- SAM radical enzymes are a diverse and important class of enzymes.
- Iron-sulfur clusters are crucial for the reduction of SAM.
- Structural data provide a framework for understanding enzyme mechanisms.