Substrate spectrum of mandelate racemase: Part 1: Variation of the α-hydroxy acid moiety

Enzymatic racemization of mandelic acid derivatives modified at the α-hydroxy acid moiety was achieved using mandelate racemase [EC 5.1.2.2]. Whereas α-amino acid derivatives, such as phenyl glycine and mandelic acid hydrazide were not accepted, the mandelic acid amide was racemized at an acceptable rate. The latter was significantly enhanced by an electron-withdrawing substituent in the phenyl moiety. Based on the catalytic mechanism of the enzyme, the relative activities of non-natural substrates could be explained by steric and electronic reasons.