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

Enzymatic racemization of mandelic acid derivatives modified at the a-hydro xy acid moiety was achieved using mandelate racemase [EC 5.1.2.2]. Whereas a-amino acid derivatives, such as phenyl glycine and mandelic acid hydrazid e were not accepted, the mandelic acid amide was racemized at an acceptable rate. The latter was significantly enhanced by an electron-withdrawing sub stituent in the phenyl moiety. Based on the catalytic mechanism of the enzy me, the relative activities of non-natural substrates could be explained by steric and electronic reasons. (C) 2001 Elsevier Science B.V. All rights r eserved.