Structural highlights
Function[4OT1_PSEPU] Catalyzes the ketonization of 2-hydroxymuconate stereoselectively to yield 2-oxo-3-hexenedioate.[1] Publication Abstract from PubMedThe enzyme 4-oxalocrotonate tautomerase (4-OT), which has a catalytic N-terminal proline residue (Pro1), can promiscuously catalyze various carbon-carbon bond-forming reactions, including aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde, and Michael-type addition of acetaldehyde to a wide variety of nitroalkenes to yield valuable gamma-nitroaldehydes. To gain insight into how 4-OT catalyzes these unnatural reactions, we carried out exchange studies in D2 O, and X-ray crystallography studies. The former established that H-D exchange within acetaldehyde is catalyzed by 4-OT and that the Pro1 residue is crucial for this activity. The latter showed that Pro1 of 4-OT had reacted with acetaldehyde to give an enamine species. These results provide evidence of the mechanism of the 4-OT-catalyzed aldol and Michael-type addition reactions in which acetaldehyde is activated for nucleophilic addition by Pro1-dependent formation of an enamine intermediate. Evidence for the Formation of an Enamine Species during Aldol and Michael-type Addition Reactions Promiscuously Catalyzed by 4-Oxalocrotonate Tautomerase.,Poddar H, Rahimi M, Geertsema EM, Thunnissen AM, Poelarends GJ Chembiochem. 2015 Feb 26. doi: 10.1002/cbic.201402687. PMID:25728471[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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