The role of lysine 166 in the mechanism of mandelate racemase from Pseudomonas putida: mechanistic and crystallographic evidence for stereospecific alkylation by (R)-alpha-phenylglycidate.

The mechanism of irreversible inactivation of mandelate racemase (MR) from Pseudomonas putida by α-phenylglycidate (αPGA) has been investigated stereochemically and crystallographically. The (R) and (S) enantiomers of αPGA were synthesized in high enantiomeric excess (81% ee and 83% ee, respectively) using Sharpless epoxidation chemistry. (R)-αPGA was determined to be a stereospecific and stoichiometric irreversible inactivator of MR. (S)-αPGA does not inactivate MR and appears to bind noncovalently to the active site of MR with less affinity than that of (R)-αPGA