Stereochemistry and Mechanism of a Microbial Phenylalanine Aminomutase

摘要

The stereochemistry of a phenylalanine aminomutase (PAM) on the andrimid biosynthetic pathway in Pantoea aggfomerans (Pa) is reported. PaPAM is a member of the 4-methylidene-lH-imidazol-5(4H)-one (MlO)-depen-dent family of catalysts and isomerizes (2S)-a-phenylala-nine to (3S)-β-phenylalanine, which is the enantiomer of the product made by the mechanistically similar aminomutase TcPAM from Taxus plants. The NH_2 and pro-(3S) hydrogen groups at C_α and C_β, respectively, of the substrate are removed and interchanged completely intramolecularly with inversion of configuration at the migration centers to form β-phenylalanine. This is a contrast to the retention of configuration mechanism followed by TcPAM.