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

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.