Characterization of the Plasmodium falciparum M17 leucyl aminopeptidase. A protease involved in amino acid regulation with potential for antimalarial drug development

Amino acids generated from the catabolism of hemoglobin by intra-erythrocytic malaria parasites are not only essential for protein synthesis but also function in maintaining an osmotically stable environment, and creating a gradient by which amino acids that are rare or not present in hemoglobin are drawn into the parasite from host serum. We have proposed that a Plasmodium falciparum M17 leucyl aminopeptidase (PfLAP) generates and regulates the internal pool of free amino acids and therefore represents a target for novel antimalarial drugs. This enzyme has been expressed in insect cells as a functional 320-kDa homo-hexamer that is optimally active at neutral or alkaline pH, is dependent on metal ions for activity, and exhibits a substrate preference for N-terminally exposed hydrophobic amino acids, particularly leucine. PfLAP is produced by all stages in the intra-erythrocytic developmental cycle of malaria but was most highly expressed by trophozoites, a stage at which hemoglobin degradation and parasite protein synthesis are elevated. The enzyme was located by immunohistochemical methods and by transfecting malaria cells with a PfLAP-green fluorescent protein construct, to the cytosolic compartment of the cell at all developmental stages, including segregated merozoites. Amino acid dipeptide analogs, such as bestatin and its derivatives, are potent inhibitors of the protease and also block the growth of P. falciparum malaria parasites in culture. This study provides a biochemical basis for the antimalarial activity of aminopeptidase inhibitors. Availability of functionally active recombinant PfLAP, coupled with a simple enzymatic readout, will aid medicinal chemistry and/or high throughput approaches for the future design/discovery of new antimalarial drugs

Hydrophosphonylation of Nanoparticle Schiff Bases as a Mean for Preparation of Aminophosphonate-Functionalized

molecule

Synthèse asymétrique d'acides phosphoniques et phosphoniques cycliques

Les dérivés hétérocycliques sont incorporés dans la structure de nombreuses molécules biologiquement actives, naturelles ou de synthèse. Ce travail de thèse décrit les efforts réalisés pour développer de nouvelles voies d'accès à deux familles de ces composés hétérocycliques : les hétérocycles phosphorés et les pyrimidines. Le premier chapitre est dédié à une étude bibliographique de l'ensemble des méthodologies d'hydrophosphonylation et d'hydrophosphinylation connues à ce jour. Le second chapitre décrit nos efforts pour développer des réactions de formation de liaisons carbone-phosphore pallado-catalysées. Le dernier chapitre est consacré à la mise au point d'une synthèse originales de b-enaminones protégées et de leur utilisation pour la synthèse de pyrimidines diversement substituées.Compounds classified as heterocyclic are found in numerous natural products and molecules biogically active. The work described herein will focus on the synthesis of two families of heterocyclic compounds through two distincts synthetic pathways. The first one lays in the organophosphorus chemistry. In Chapter I, numerous methodologies known in the literature will be explained. The significance of metal-catalyzed hydrophosphonylation / hydrophosphinylation reactions will be described. Chapter II stands for the experimental exploration of metal-catalyzed intramolecular and intermolecular P-C bond formation. In Chapter III the attention will be turned to the development of a base-catalyzed synthesis of Cbz-protected b-enaminones and their subsequent implementation in the cyclization reaction towards 2,4,6-trisubstituted pyrimidines.MONTPELLIER-Ecole Nat.Chimie (341722204) / SudocSudocFranceF

Synthesis of cyclooctapeptides: constraints analogues of the peptidic neurotoxin, -agatoxin IVB - an experimental point of view

International audienceAGA IVB is an important lead structure when considering the design of effectors of glutamate release inducting P/Q type calcium channels. The best route to achieve the analogues possessing the three-dimensional arrangement corresponding to the native binding loop was the introduction of constraint by ring formation via side chain to side chain lactamization for suitably protected Lys and Glu residues. Since tryptophane residue located at position 14 of this neuropeptide has been suggested as essential for binding, analogues in which this amino acid was replaced by aza-tryptophane and alanine were synthesized. The synthesis was carried out on various acid labile (BARLOS chlorotrityl, Rink amide, PEG based or Wang resins), by Fmoc strategy. In this paper, we describe optimization of the peptide cyclization with various protecting groups, and on resin or in solution cyclization experimental parameters. Copright 2007 European Peptide Society and John Wiley & Sons Ltd

Organophosphonate Utilization by the Thermophile Geobacillus caldoxylosilyticus T20

A strain of Geobacillus caldoxylosilyticus from central heating system water could utilize a number of organophosphonates as the sole phosphorus source for growth at 60°C. During growth on glyphosate, aminomethylphosphonate release to the medium was observed, and in cell extracts, a glyphosate oxidoreductase-type activity, producing stoichiometric amounts of aminomethylphosphonate and glyoxylate from glyphosate, was detectable