4X1C:
reference: 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

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).