Biochemical Characterization of Branched Chain Amino Acids Uptake in Trypanosoma cruzi.

Trypanosoma cruzi is the etiological agent of Chagas disease. During its life cycle, it alternates among vertebrate and invertebrate hosts. Metabolic flexibility is a main biochemical characteristic of this parasite, which is able to obtain energy by oxidizing a variety of nutrients that can be transported from the extracellular medium. Moreover, several of these metabolites, more specifically amino acids, have a variety of functions beyond being sources of energy. Branched chain amino acids (BCAA), beyond their role in ATP production, are involved in sterol biosynthesis; for example, leucine is involved as a negative regulator of the parasite differentiation process occurring in the insect midgut. BCAA are essential metabolites in most nonphotosynthetic eukaryotes, including trypanosomes. In view of this, the metabolism of BCAA in T. cruzi depends mainly on their transport into the cell. In this work, we kinetically characterized the BCAA transport in T. cruzi epimastigotes. Our data point to BCAA as being transported by a single saturable transport system able to recognize leucine, isoleucine and valine. In view of this, we used leucine to further characterize this system. The transport increased linearly with temperature from 10 to 45 °C, allowing the calculation of an activation energy of 51.30 kJ/mol. Leucine uptake was an active process depending on ATP production and a H(+) gradient, but not on a Na(+) or K(+) gradient at the cytoplasmic membrane level.

A benzoic acid derivative and flavokawains from Piper species as schistosomiasis vector controls.

The search of alternative compounds to control tropical diseases such as schistosomiasis has pointed to secondary metabolites derived from natural sources. Piper species are candidates in strategies to control the transmission of schistosomiasis due to their production of molluscicidal compounds. A new benzoic acid derivative and three flavokawains from Piper diospyrifolium, P. cumanense and P. gaudichaudianum displayed significant activities against Biomphalaria glabrata snails. Additionally, "in silico" studies were performed using docking assays and Molecular Interaction Fields to evaluate the physical-chemical differences among the compounds in order to characterize the observed activities of the test compounds against Biomphalaria glabrata snails.

Application of bioisosterism in design of the semicarbazone derivatives as cruzain inhibitors: a theoretical and experimental study.

A series of semicarbazone, thiosemicarbazone, and aminoguanidine derivatives were synthesized and tested as antitrypanosomal agents. The theoretical NMR of the compounds was calculated using molecular modeling techniques (density functional theory (DFT) calculations) and confirmed the formation of the compounds. The ability to inhibit cruzain and Trypanosoma cruzi epimastigote replication was evaluated. Cruzain inhibition ranged between 70 and 75% (100 µM), and IC50 values observed in epimastigote forms of T. cruzi ranged from 20 to 140 µM. Furthermore, the compounds did not present cytotoxicity at concentrations up to 50 and 250 µM in MTT tests. Molecular modeling studies were conducted using DFT method (B3LYP functional and the basis set 6-311G(d,p)) to understand the activity of the compounds, corroborating the observed cruzain inhibitory activity. In docking studies, the obtained analogs showed good complementarity with cruzain active site. In addition, docking results are in accordance with the susceptibility of these analogs to nucleophilic attack of the catalytic Cys25. Taken together, this study shows that this class of compounds can be used as a prototype in the identification of new antichagasic drugs.