The occurrence of free d-alanine and an alanine racemase activity inLeishmania amazonensis

Abstract

Free D-amino acids are implicated in several biological functions. This study examined the presence of D-alanine in Leishmania amazonensis. Measuring chiral amino acid content by high-performance liquid chromatography we detected a significant amount of free D-alanine in promastigotes of these parasites. D-alanine accounts for 8.9% of total free alanine and is found primarily in the soluble fraction. Specific racemization of L-alanine to D-alanine was detected in cell lysates and this enzyme activity was inhibited by D-cycloserine, an alanine racemase inhibitor. Furthermore, we were able to decrease this pool of D-amino acid by treating our cultures with D-cycloserine. We demonstrate for the first time the existence of a significant amount of free D-alanine in L. amazonensis and an alanine racemase activity present in cell lysates. The restriction of D-alanine to bacteria, some fungi and now in L. amazonensis opens a new perspective on treatment of diseases caused by these microorganisms.

Systems analysis of metabolism in the pathogenic trypanosomatid Leishmania major

“…As an example of a hypothetical gene annotation refinement, consider LmjF23.1480 , which this study characterizes as an ‘alanine racemase.’ D ‐Alanine was included as a substrate in the experimentally defined medium provided in Merlen et al (1999); Schuster and Sullivan (2002). This was the first indication that the L. major genome coded for a racemase that converted D ‐alanine into L ‐alanine, the latter isomer required for protein synthesis (Panizzutti et al , 2006). However, there were no L. major genes in KEGG (http://www.genome.jp/kegg/) or GeneDB (http://www.genedb.org/) annotated as ‘alanine racemase.’ Moreover, two Trypanosoma cruzi genes that coded for alanine racemase were found.…”

Ultraviolet radiation induces stress in etiolated Landoltia punctata, as evidenced by the presence of alanine, a universal stress signal: a 15N NMR study

“…Several D-amino acids have been detected in higher plants (Ogawa 1976;Robinson 1976), and D-alanine is widely distributed in leaves of rice (Manabe & Ohira 1984), pea seedlings, N. tabacum (Gisby et al 2012) and A. thaliana (G€ ordes et al 2013). Only in the plant kingdom is the metabolism and role of D-amino acids still unclear, although plants must cope with significant amounts of these compounds in the rhizosphere (Panizzutti et al 2006). According to Manabe & Ohira (1984), D-alanine in tissues is not the result of microbial contamination, but is produced by the infected plants themselves; moreover, racemase activity, which converts exogenous L-alanine to D-alanine, has been detected in plant tissues.…”

The Uptake and Metabolism of Amino Acids, and Their Unique Role in the Biology of Pathogenic Trypanosomatids

“…It has been demonstrated in Leishmania that approximately 90% of the free Ala pool corresponds to the L-isomer. The remaining part is formed by D-Ala that is synthesized by the activity of the Ala racemase [ 262 ] (AlaR, EC 5.1.1.1). Putative coding sequences for Ala racemase are present in both the T. cruzi and T. brucei genomes, but they still remain uncharacterized.…”