Various d-amino acids, such as D-serine, D-aspartic acid (D-Asp), and D-glutamic acid (D-Glu) are widely found in mammals including human beings and they are now thought to be the candidates of novel physiologically active substances and/or biomarkers. D-[Asp/Glu] (4 mg/mL) inhibits IgE binding (75%) to peanuts while D-Glu, D-Asp has no inhibitory effect. IgE is specific for D-[Asp/Glu] and may have the potential for removing IgE or reducing IgE binding to peanut allergens.

D-glutamic acid is currently paid attention as a modulator of neuronal transmission and hormonal secretion. It is metabolized only by D-aspartate oxidase in mammals. After intraperitoneal injection, L-glutamate is catabolized via a-ketoglutarate, whereas D-glutamate is converted to n-pyrrolidone carboxylic acid. Carbon 2 of both D- and L-glutamate is converted in the cecum to the methyl carbon of acetate. Both rat liver and kidney catalyze the conversion of D-glutamic acid to n-pyrrolidone carboxylic acid.