InterPro domain: IPR015942

This entry represents a group of related proteins that includes aspartate racemase, glutamate racemase, hydantoin racemase and arylmalonate decarboxylase. Two conserved cysteines are present in the sequence of these enzymes. They play a role in catalytic activity by acting as bases in proton abstraction from the substrate [ 1 , 2 , 3 ].

Aspartate racemase ( 5.1.1.13 ) and glutamate racemase ( 5.1.1.3 ) are two evolutionary related bacterial enzymes that do not seem to require a cofactor for their activity [ 4 ]. Glutamate racemase, which interconverts L-glutamate into D-glutamate, is required for the biosynthesis of peptidoglycan and some peptide-based antibiotics such as gramicidin S. The E.coli L-aspartate/glutamate specific racemase Ygea, which was previously an hypothetical protein, has been shown to have racemase activity for both L-glutamate and L-aspartate with higher preference for L-glutamate [ 5 ].

Hydantoin racemases catalyse the racemization of various 5-substituted hydantoins. The structure of the allantoin racemase from Klebsiella pneumoniae has been solved [ 5 ].

1. Site-directed mutagenesis indicates an important role of cysteines 76 and 181 in the catalysis of hydantoin racemase from Sinorhizobium meliloti. Protein Sci. 15, 2729-38
2. Characterization of the Structure and Function of Klebsiella pneumoniae Allantoin Racemase. J. Mol. Biol. 410, 447-60
3. Structural basis for an atypical active site of an L-aspartate/glutamate-specific racemase from Escherichia coli. FEBS Lett. 589, 3842-7
4. Purification, cloning, and cofactor independence of glutamate racemase from Lactobacillus. Biochemistry 32, 3981-90