The presence of free D-serine, D-alanine and D-proline in human plasma

Abstract

Twelve neutral free amino acids, i.e. serine, threonine, glutamine, asparagine, alanine, proline, methionine, tyrosine, valine, leucine, isoleucine and phenylalanine, were surveyed for the presence of D-enantiomers in plasma samples from patients with renal diseases and from normal subjects. D-serine, D-alanine and D-proline were found in the patient's plasma. The highest concentrations (D/L ratio) of D-serine, D-alanine and D-proline were 0.2362, 0.2087 and 0.0986, respectively. The sum of the contents of the three D-amino acid was shown to be present in the plasma proteins.

Preferred Stereoselective Transport of the D-isomer of cis-4-[18F]fluoro-proline at the Blood–Brain Barrier

“…In addition, D-amino acids are synthesized in vivo by microorganisms by transformation of L-isomers, which are enzymatically catalyzed by amino-acid oxidases, transaminases and racemases (Friedman, 1999). The concentration of D-proline in the human plasma is low and less than 1% of the concentration of L-proline, which ranges from 40 to 150 mmol/L plasma (Nagata et al, 1992;Bruckner and Hausch, 1993). D-proline is partly renally excreted in its unmetabolized form and effectively oxidized by D-amino-acid oxidase to a-keto-d-amino-valeric acid, which is further metabolized (Schieber et al, 1996).…”

Sensitive Determination of D-Amino Acids in Mammals and the Effect of D-Amino-Acid Oxidase Activity on Their Amounts

“…[1][2][3] and recently, it was reported that D-Ala has the relationship with various diseases in mammals. [16][17][18][19] Therefore, for the investigation of 44) and Boc-L-Cys 22,45,46) have been reported. Our method 22) using Boc-L-Cys is an improvement of the method reported by Hashimoto et al 46) The analytical conditions were examined using the cerebellum of a normal ddY/DAO ϩ mouse, the tissue having a high DAO activity, from which the amounts of the naturally occurring D-amino acids are small.…”

“…[10][11][12][13][14][15] The D-alanine (D-Ala) amounts have also been reported to change in the case of diseases. [16][17][18][19] Though the D-amino acids are being noticed as the candidates of physiologically active substances, the determination of most Damino acids is difficult because their amounts in mammalian tissues are extremely low and various interfering substances are present in the tissues. In addition, their functions, origins and regulation mechanisms still remain unknown for the most part.…”

Effects of D-Amino Acid Oxidase Inhibitor on the Extracellular D-Alanine Levels and the Efficacy of D-Alanine on Dizocilpine-Induced Prepulse Inhibition Deficits in Mice

“…D-Alanine is the first D-amino acid found in serum of guinea pig and mice [16]. Subsequent studies demonstrated that free D-alanine is one of the D-amino acids naturally occurring in the mammalian tissues including brain and blood [17][18][19][20][21][22]. D-Alanine, like D-serine, is also a selective and potent agonist at the glycine-modulatory site on the NMDA receptors [23][24][25].…”