Related Experiment Video
Updated: Jun 8, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
S-Adenosylmethionine-dependent radical-based modification of biological macromolecules
Mohamed Atta1, Etienne Mulliez, Simon Arragain
1Institut de Recherches en Technologie et Sciences pour le Vivant IRTSV-LCBM, UMR 5249 CEA/CNRS/UJF, CEA-Grenoble, 17 avenue des Martyrs, 38054 Grenoble Cedex 09, France.
Abstract:
Proteins and RNA molecules enjoy a variety of chemically complex post-translational and post-transcriptional modifications. The chemistry at work in these reactions, which was considered to be exclusively ionic in nature has recently been shown to depend on radical mechanisms in some cases. The overwhelming majority of these radical-based reactions are catalyzed by 'Radical-SAM' enzymes. This review article highlights mechanistic and structural aspects of this class of reactions and indicates important research directions to be addressed.
Related Concept Videos
RNA Editing
Phase II Reactions: Methylation Reactions
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
Radical Reactivity: Overview
Radical Formation: Addition
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an unpaired...
Radical Reactivity: Nucleophilic Radicals
Transfer RNA Synthesis
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...

