We report that D-N-hydroxyglutamate is a competitive inhibitor of glutamate racemase (KI = 56 ~VI). The compound acts as an alternate substrate and is converted into c~-ketoglutarate and ammonia (KM = 57 ~tM, kcat/KM = 3.2 X 103 M-lsec-l). An imine intermediate is likely the species causing the inhibition. 1.-Nhydroxyglutamate is a weak inhibitor and is slowly converted to ct-ketoglutarate (kcat/KM = 30 M-lsec -1 ).