Pyruvate-dependent aldolases reactions catalyzed

Pyruvate-dependent aldolases catalyze the breaking of a carbon-carbon bond in nature. This reaction can, however, be reversed if an excess of pyruvate is used, establishing one new stereocenter in the course of it. The natural function of phosphoenolpyruvate (PEP)-dependent aldolases on the other hand is to catalyze the synthesis of a-keto acids. Since PEP is a very reactive, unstable and difficult to prepare substrate, they are not commonly used in synthesis. 

Scheme 5.27. Pyruvate-dependent aldolases and the reactions they catalyze. P = PO32. ...

Class II pyruvate-dependent 4-hydroxy-2-oxopentanoate aldolases (EC 4.1.2.-), BphI and Hpal, catalyze the retroaldol reactions of 4-hydroxy-2-oxopentanoate (43) to p5uiivate (1) and acetaldehyde and 4-hydroxy-2-oxo-l,7-heptanedioate (44) to 1 and succinic semialdehyde (45) (Scheme 10.7) [45,96]. BphI is selective for (S)-43 stereoisomer, whereas Hpal accepts both enantiomers [97]. 

---