We have produced a portfolio of robust designer enzymes (amino acid dehydrogenases) using structural information and genetic techniques. These will handle a wide range of commercially-interesting substrates. The enzymes can be used in either one of two ways to produce chiral amino acid building blocks for drug synthesis. If the keto acid is most readily available by chemical synthesis, these enzymes will introduce the chiral amino group with 100% fidelity.  If instead a 50:50 racemic mixture of D and L amino acids is more cheaply available, the enzymes can be used in two stages to effect a total separation of the two isomers.