The presence of high concentrations of free D-amino acids in human saliva.
Free neutral D-amino acids have previously been detected in human plasma, usually accounting for less than 2% of the total free amino acid concentration (D-amino acid ratio) [Nagata, Y., Masui, R., Akino, T., 1992a. The presence of free D-serine, D-alanine and D-proline in human plasma. Experientia 48, 986-988. Nagata, Y., Yamamoto, K., Shimojo, T., 1992b. Determination of D- and L-amino acids in mouse kidney by high-performance liquid chromatography. Journal of Chromatography 575, 147-152. Nagata, Y., Yamamoto, K., Shimojo, T., Konno, R., Yasumura, Y., Akino, T., 1992c. The presence of free D-alanine, D-proline and D-serine in mice. Biochimca et Biiophysica Acta 1115, 208-211]. In the present study to search for the source of free D-amino acids, D- and L-enantiomers of the major non-essential amino acids, i.e., the free form of serine, alanine, proline, aspartate and glutamate were analyzed by HPLC in human saliva, submandibular glands and oral epithelial cells. The D-enantiomer ratios to total of free alanine or proline were 35% and 20%, respectively, in saliva. The ratios of the other D-amino acids were less than 11%. The effect of ingested food and oral bacteria on the saliva amino acid levels was suggested to be insignificant. D-Alanine and d-aspartate were also detected in the submandibular gland in ratios up to 5%, and D-alanine and d-proline were found in oral epithelial cells in ratios of 18% and 5%, respectively. The submandibular gland and oral epithelial cells are suggested to be possible sources of the saliva D-alanine and D-aspartate.
Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308, Japan. nagata@chem.cst.nihon-u.ac.jp
Yoko
Y
Nagata
Masatoshi
M
Higashi
Yutaka
Y
Ishii
Hiroaki
H
Sano
Minoru
M
Tanigawa
Kumiko
K
Nagata
Kazuma
K
Noguchi
Masahiro
M
Urade
D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003605:D-Amino-Acid Oxidase / Q000096:biosynthesis; D004847:Epithelial Cells / Q000201:enzymology / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000166:cytology / Q000201:enzymology / Q000382:microbiology; D012463:Saliva / Q000737:chemistry* / Q000382:microbiology; D013237:Stereoisomerism; D013363:Submandibular Gland / Q000201:enzymology
D000596:Amino Acids; D003605:D-Amino-Acid Oxidase