Ammonia-lyases catalyze a wide range of processes leading to alpha,beta-unsaturated
compounds by elimination of ammonia. In this chapter, ammonia-lyases are reviewed
with major emphasis on their synthetic applications in stereoselective preparation
of unnatural amino acids. Besides the synthesis of various
unnatural alpha-amino acids with the aid of phenylalanine ammonia-lyases (PALs) utilizing
the 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) prosthetic groups, the biotransformations
leading to various unnatural beta-amino acids with phenylalanine 2,3-aminomutases
using the same catalytic MIO prosthetic group are discussed. Cloning, production,
purification, and biotransformation protocols for PAL are described in detail.
