Yoshikawa Masanobu, Kan Takugi, Shirose Kosuke, Watanabe Mariko, Matsuda Mitsumasa, Ito Kenji, Kawaguchi Mitsuru
Department of Clinical Pharmacology, School of Medicine, Tokai University, Isehara 259-1193, Japan.
Department of Anesthesiology, School of Medicine, Tokai University, Isehara 259-1193, Japan.
Biology (Basel). 2022 Mar 2;11(3):390. doi: 10.3390/biology11030390.
Free d-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 -methyl-d-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.
游离的d-氨基酸是l-氨基酸的对映体，存在于包括人类在内的哺乳动物中，并在中枢神经系统和外周组织的一系列生理功能中发挥重要作用。在唾液中已观察到几种d-氨基酸，但其来源以及参与其代谢和分解代谢的酶仍有待阐明。在本研究中，在大鼠的所有三大唾液腺中均检测到大量的d-天冬氨酸以及少量的d-丝氨酸和d-丙氨酸。未检测到其他d-对映体。在所有三种类型的唾液腺中均检测到d-氨基酸氧化酶和d-天冬氨酸氧化酶的蛋白表达，这两种酶分别负责中性和二羧酸d-氨基酸的氧化脱氨作用。此外，腮腺中d-丝氨酸代谢酶丝氨酸消旋酶的蛋白表达量约为大脑皮层中观察到的表达量的40%。在所有三大唾液腺中均检测到N-甲基-d-天冬氨酸亚基蛋白NR1和NR2D。本研究结果表明，d-氨基酸在唾液腺的一系列内分泌和外分泌功能中发挥生理作用。
