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Radical Enzymes

  1. Britt-Marie Sjöberg,
  2. Margareta Sahlin

Published Online: 23 SEP 2005

DOI: 10.1038/npg.els.0003889



How to Cite

Sjöberg, B.-M. and Sahlin, M. 2005. Radical Enzymes. eLS. .

Author Information

  1. Stockholm University, Stockholm, Sweden

Publication History

  1. Published Online: 23 SEP 2005


Radical enzymes harbour a stable free radical in their polypeptide chain, which participates in catalysis. A growing number of enzymes are known to require a posttranslationally generated free radical for their proper functioning. The radical is generally used to remove a hydrogen atom from an unreactive position in the substrate, activating the substrate to undergo difficult chemistry. Some radical enzymes have unexpectedly been found to harbour a stable radical on an amino acid side-chain that is distinct from the side-chains of the active site region; during catalysis, the stable free radical interacts with the active site via electron or radical transfer and between turnovers it serves as a radical sink.


  • tyrosyl radical;
  • glycyl radical;
  • cysteinyl radical;
  • ribonucleotide reductase