Threonine aldolases.

Threonine aldolases catalyze the pyridoxal phosphate-dependent condensation between small amino acids (principally glycine) and aldehydes such as acetaldehyde. Carbon-carbon bond formation involves forming two adjacent chiral centers. As a rule, threonine aldolases are very stereoselective for α-carbon configuration but show modest selectivity at the β-carbon. On the other hand, these enzymes accept a wide variety of synthetically useful acceptor aldehydes, making them important additions to the synthetic toolkit. This review briefly summarizes the reaction mechanism and then lists all published synthetic reactions by threonine aldolases as of early 2014. The current state of the art in crystallographic and protein engineering studies of these enzymes is also presented.