Functional characterization of malic enzymes in Leishmania parasites

GIORDANA LUCILA; NOWICKI CRISTINA

Mar del Plata

Congreso; X Congreso de Protozoología y enfermedades parasitarias; 2014

Sociedad Argentina de Protozoología

Leishmania spp. like trypanosomes are notably sensitive against oxidative stress. For survival these pathogens depend on a complex redox cascade which utilizes the reducing equivalents derived from trypanothione T(SH2). The latter is maintained on its reduced form by trypanothione reductase. This enzyme exclusively relays on NADPH as electron source. Consequently, NADPH is consumed at high rates and its production is essential for parasite survival. Even though pentose phosphate pathway is considered a good candidate for the supply of the reduced coenzyme,Leishmania amastigotes are believed to develop in a glucose deprived environment. Therefore, these pathogens are expected to count on alternative sources for NADPH production,such as malic enzymes (MEs). Among trypanosomatids, MEs have been only characterized in pathogenic trypanosomes like Trypanosoma cruzi and Trypanosoma brucei.T. cruzi presents two functional isoforms, one localized in the cytosoland other in the mitochondrion. The cytosolic ME is expressed only in promastigotes and it is activated by L-aspartate. By contrast the relative abundance of the mitochondrial ME, is notably increased in T. cruzi amastigotes [Leroux, et. al., 2011].The survey of the sequenced genomes of Leishmania species put in evidence that L. major exhibited a single gene coding for a putative ME (ME_Lmj),while L. mexicana,L. infantum and L. braziliensis displayed two putative gene copies encoding ME isoform(s), ME_1 and ME_2. The sequence identity between ME_1 and ME_2 is about 60%, while the putative ME_Lmj is >95 % identical to ME_1. To shed light on the biochemical properties of leishmanial MEs we have cloned and expressed in E. coli the putative ME_Lmj in addition to ME_1 and ME_2 fromL. mexicana