Substrate-assisted catalysis in sialic acid aldolase

The reversible aldol condensation of pyruvate and N-acetylmannosamine is catalyzed by sialic acid aldolase with an apparent lack of stereospecificity. As part of this reaction, two conformations are formed from the modeling of Schiff base and enamine intermediates in the active site of the protein. The acceptor-aldehyde group is located in different sides of the enamine in the conformations, although the remainder of the substrate has extremely similar geometries.