5.1.2.2 A25V Catalytic efficiencies (kcat/Km) for all mutants are reduced between 6- and 40fold with the exception of V22I, V26A, V29L, and V22I/V29L which have near wildtype efficiencies with mandelate 690962 5.1.2.2 A25V site-directed mutagenesis 726974 5.1.2.2 A25V variation of the hydrophobic loop, decrease in catalytic efficiency 690962 5.1.2.2 C92S/C264S/K166C site-directed mutagenesis 727042 5.1.2.2 D270N structure of D270N with (S)-atrolactate bound in the active site reveals no geometric alterations when compared to the structure of the wild type enzyme complexed with (S)-atrolactate, with the exception that the side chain of His297 is tilted and displaced about 0.5A away from Asn270 and towards the (S)-atrolactate. The turnover number for both (R)-mandelate and (S)-mandelate are reduced 10000fold 285178 5.1.2.2 E317Q E317Q with 3400fold reduced turnover number for (R)-mandelate and 29000fold reduced turnover number for (S)-mandelate. E317Q mutant enzyme does not catalyze detectable elimination of Br- from either enantiomer of p-(bromomethyl)mandelate. E317Q mutant enzyme is irreversibly inactivated by racemic alpha-phenylglycidate at a rate comparable to that measured for wild type enzyme 285194 5.1.2.2 F52W compared to wild-type enzyme the catalytic preference of the mutant enzyme is reversed and catalytic efficiency is reduced. Mutant enzyme exhibits higher affinity for (R)-mandelate than for (S)-mandelate, and a higher turnover number with (S)-mandelate as the substrate, relative to that with (R)-mandelate 661212 5.1.2.2 F52W/Y54W compared to wild-type enzyme the catalytic preference of the mutant enzyme is reversed and catalytic efficiency is reduced. Mutant enzyme exhibits higher affinity for (R)-mandelate than for (S)-mandelate, and a higher turnover number with (S)-mandelate as the substrate, relative to that with (R)-mandelate 661212 5.1.2.2 H297N H297N has no detectable mandelate racemase activity. However, H297N catalyzes the stereospecific elimination of Br- from racemic p-(bromomethyl)mandelate to give p-(methyl)benzoylformate in 45% yield at a rate equal to that measured for wild type enzyme 285186 5.1.2.2 H297N H297N, which is inactive as a racemase catalyzes the stereospecific exchange of the alpha-proton of S- but not R-mandelate with solvent D2O at a rate that is 30% of that of the wild type enzyme 285189