63 research outputs found
A Key Role for Old Yellow Enzyme in the Metabolism of Drugs by Trypanosoma cruzi
Trypanosoma cruzi is the etiological agent of Chagas' disease. So far, first choice anti-chagasic drugs in use have been shown to have undesirable side effects in addition to the emergence of parasite resistance and the lack of prospect for vaccine against T. cruzi infection. Thus, the isolation and characterization of molecules essential in parasite metabolism of the anti-chagasic drugs are fundamental for the development of new strategies for rational drug design and/or the improvement of the current chemotherapy. While searching for a prostaglandin (PG) F2α synthase homologue, we have identified a novel âold yellow enzymeâ from T. cruzi (TcOYE), cloned its cDNA, and overexpressed the recombinant enzyme. Here, we show that TcOYE reduced 9,11-endoperoxide PGH2 to PGF2α as well as a variety of trypanocidal drugs. By electron spin resonance experiments, we found that TcOYE specifically catalyzed one-electron reduction of menadione and ÎČ-lapachone to semiquinone-free radicals with concomitant generation of superoxide radical anions, while catalyzing solely the two-electron reduction of nifurtimox and 4-nitroquinoline-N-oxide drugs without free radical production. Interestingly, immunoprecipitation experiments revealed that anti-TcOYE polyclonal antibody abolished major reductase activities of the lysates toward these drugs, identifying TcOYE as a key drug-metabolizing enzyme by which quinone drugs have their mechanism of action
The role of laccase in prostaglandin production by Cryptococcus neoformans
Recently, it has been demonstrated that the opportunistic fungal pathogen Cryptococcus neoformans can synthesize authentic immunomodulatory prostaglandins. The mechanism by which this takes place is unclear as there is no cyclooxygenase homologue in the cryptococcal genome. In this study, we show that cryptococcal production of both PGE 2 and PGF 2α can be chemically inhibited by caffeic acid, resveratrol and nordihydroguaiaretic acid. These polyphenolic molecules are frequently used as inhibitors of lipoxygenase enzymes; however, blast searches of the cryptococcal genome were unable to identify any homologues of mammalian, plant or fungal lipoxygenases. Next we investigated cryptococcal laccase, an enzyme known to bind polyphenols, and found that either antibody depletion or genetic deletion of the primary cryptococcal laccase ( lac1 Ύ) resulted in a loss of cryptococcal prostaglandin production. To determine how laccase is involved, we tested recombinant laccase activity on the prostaglandin precursors, arachidonic acid (AA), PGG 2 and PGH 2 . Using mass spectroscopy we determined that recombinant Lac1 does not modify AA or PGH 2 , but does have a marked activity toward PGG 2 converting it to PGE 2 and 15-keto-PGE 2 . These data demonstrate a critical role for laccase in cryptococcal prostaglandin production, and provides insight into a new and unique fungal prostaglandin pathway.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73041/1/j.1365-2958.2008.06245.x.pd
A role for trypanosomatid aldo-keto reductases in methylglyoxal, prostaglandin and isoprostane metabolism
Late Stage Infection in Sleeping Sickness
At the turn of the 19th century, trypanosomes were identified as the causative agent of sleeping sickness and their presence within the cerebrospinal fluid of late stage sleeping sickness patients was described. However, no definitive proof of how the parasites reach the brain has been presented so far. Analyzing electron micrographs prepared from rodent brains more than 20 days after infection, we present here conclusive evidence that the parasites first enter the brain via the choroid plexus from where they penetrate the epithelial cell layer to reach the ventricular system. Adversely, no trypanosomes were observed within the parenchyma outside blood vessels. We also show that brain infection depends on the formation of long slender trypanosomes and that the cerebrospinal fluid as well as the stroma of the choroid plexus is a hostile environment for the survival of trypanosomes, which enter the pial space including the Virchow-Robin space via the subarachnoid space to escape degradation. Our data suggest that trypanosomes do not intend to colonize the brain but reside near or within the glia limitans, from where they can re-populate blood vessels and disrupt the sleep wake cycles
AEROMONAS CAVIAE ME-1 XYLANASES : Biochemical Studies, Biotechnological Utilization and Analysis of Xylanase(s) Geme
Prééminence de YHWH ou autonomie du prophÚte: Etude comparative et critique des confessions de Jérémie dans le texte hébreu massorétique et la "Septante"
A la suite dâimportantes dĂ©couvertes Ă QumrĂąn (et dans le dĂ©sert de Juda) de nombreux manuscrits bibliques et de leur publication progressive, plusieurs chercheurs ont voulu saisir lâoccasion qui sâoffrait ainsi pour reprendre Ă nouveaux frais lâĂ©tude de la LXX et rĂ©affirmer son importance pour lâexĂ©gĂšse et sa place dans la comprĂ©hension de lâhistoire la plus ancienne du texte biblique.
La prĂ©sente Ă©tude des confessions de JĂ©rĂ©mie (on en dĂ©nombre habituellement 5 : Jr 11,18-12,6 ; 15,10-21 ; 17,12-18 ; 18,18-23 et 20,7-18) sâinscrit dans le cadre de cet effort scientifique qui tente de dĂ©terminer les rapports entre la LXX et le TM du livre de JĂ©rĂ©mie. Le regard rĂ©trospectif sur lâhistoire de la recherche et la discussion sur la datation de la forme longue du livre de JĂ©rĂ©mie qui en dĂ©coule (chap. 1) vise Ă Ă©clairer les diffĂ©rentes tendances majeures dans les travaux qui se consacrent Ă lâĂ©tude du livre de JĂ©rĂ©mie. La partie centrale du livre (chap. 2) est consacrĂ©e Ă une Ă©tude comparative et critique dĂ©taillĂ©e de la forme textuelle hĂ©braĂŻque en TM et la forme textuelle de la LXX, dans le but de vĂ©rifier si le texte des confessions de JĂ©rĂ©mie est proche ou Ă©loignĂ© dans les deux formes textuelles (TM et LXX). Nous cherchons ensuite Ă mettre en lumiĂšre (chap. 3), par une analyse approfondie de certains choix textuels opĂ©rĂ©s par chacune des deux formes textuelles, la maniĂšre propre dont chacune prĂ©sente ou caractĂ©rise le personnage de JĂ©rĂ©mie. Dans le dernier chapitre (chap. 4), nous nous demandons si lâĂ©tude des confessions peut Ă©clairer le rapport chronologique (dâantĂ©rioritĂ© ou de postĂ©rioritĂ©) entre les deux formes textuelles et aider Ă Ă©tablir un rapport de prioritĂ© de lâune par rapport Ă lâautre de ces deux formes textuelles et, Ă©ventuellement, de suggĂ©rer leur datation.
Il ressort de cette Ă©tude synoptique minutieuse et critique faite sur les confessions que, de maniĂšre gĂ©nĂ©rale, les deux formes textuelles y reprĂ©sentent un texte commun. Le livre de JĂ©rĂ©mie semble avoir gardĂ© dans le TM comme dans la LXX des traces, des passages importants dâun livre conçu initialement pour ĂȘtre un seul et mĂȘme livre. NĂ©anmoins, les quelques diffĂ©rences (de type textuel et rĂ©dactionnel ou de type littĂ©raire) relevĂ©es entre les deux formes textuelles (TM et LXX) dans les confessions ont permis de mettre en lumiĂšre le mouvement qui a surtout vu le texte Ă©voluer du modĂšle hĂ©breu de la LXX vers le texte hĂ©breu massorĂ©tique. Quant Ă savoir quand et par qui ces retouches rĂ©dactionnelles ont Ă©tĂ© opĂ©rĂ©es, les indices relevĂ©s dans les textes parlent en faveur de la pĂ©riode ayant immĂ©diatement suivi la fin de lâexil babylonien (Ă savoir la fin du 6e et le dĂ©but du 5e siĂšcle avant J.-C.) comme Ă©tant le moment le plus propice pour une activitĂ© littĂ©raire dâune telle envergure
AEROMONAS CAVIAE ME-1 XYLANASES : Biochemical Studies, Biotechnological Utilization and Analysis of Xylanase(s) Geme
[Rezension von: Kilunga, Godefroid Bambi, 1962-, Prééminence de YHWH ou autonomie du prophÚte]
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