-amino acids, which are enantiomers of l
-amino acids, are found in mammals, including humans, and play an important role in a range of physiological functions in the central nervous system and peripheral tissues. Several d
-amino acids have been observed in saliva, but their origin and the enzymes involved in their metabolism and catabolism remain to be clarified. In the present study, large amounts of d
-aspartic acid and small amounts of d
-serine and d
-alanine were detected in all three major salivary glands in rat. No other d
-enantiomers were detected. Protein expression of d
-amino acid oxidase and d
-aspartate oxidase, the enzymes responsible for the oxidative deamination of neutral and dicarboxylic d
-amino acids, respectively, were detected in all three types of salivary gland. Furthermore, protein expression of the d
-serine metabolic enzyme, serine racemase, in parotid glands amounted to approximately 40% of that observed in the cerebral cortex. The N
-aspartic acid subunit proteins NR1 and NR2D were detected in all three major salivary glands. The results of the present study suggest that d
-amino acids play a physiological role in a range of endocrine and exocrine function in salivary glands.
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