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Updated: Aug 21, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Enzymatic reactions involving novel mechanisms of carbanion stabilization
Tadhg P Begley1, Steven E Ealick
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, NY14853, USA. tpb2@cornell.edu
Abstract:
The reactions catalyzed by orotidine monophosphate decarboxylase, oxalate decarboxylase, organomercurial lyase and phosphopantothenoylcysteine decarboxylase involve putative high-energy carbanion intermediates that cannot be stabilized by delocalization. Mechanistic and structural studies on each of these enzymes are described that suggest different strategies for carbanion stabilization. Both orotidine monophosphate decarboxylase and organomercurial lyase are likely to avoid carbanion formation by protonating the fragmenting bond, oxalate decarboxylase stabilizes an acyl carbanion using an adjacent radical and phosphopantothenoylcysteine decarboxylase stabilizes its carbanion by delocalization into a transient thioaldehyde.
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