Diversity of microbial threonine aldolases and their application

Threonine aldolase catalyzes the reversible interconversion of certain β-hydroxy-α-amino acids and glycine plus the corresponding aldehydes. Various microbial threonine aldolases with different stereospecificities were found on extensive screening, and the genes encoding the proteins were cloned and heterogeneously overexpressed in Escherichia coli. By using recombinant threonine aldolases, an enzymatic resolution process was established for the production of optically pure β-hydroxy-α-amino acids. In addition, the threonine aldolase-catalyzed direct synthesis of β-hydroxy-α-amino acid from aldehyde and glycine is discussed.