This invention relates generally to enzymes, polynucleotides encoding the enzymes having isomerase activity, e.g., racemase activity, e.g., amino acid racemase activity, alanine racemase activity, and/or epimerase activity, and/or catalyze the re-arrangement of atoms within a molecule, catalyze the conversion of one isomer into another, catalyze the conversion of an optically active substrate into a raceme, which is optically inactive, catalyze the interconversion of substrate enantiomers, catalyze the stereochemical inversion around the asymmetric carbon atom in a substrate having only one center of asymmetry, catalyze the stereochemical inversion of the configuration around an asymmetric carbon atom in a substrate having more than one asymmetric center, and/or catalyze the racemization of amino acids.