Saturday, May 16, 2009

What's new for 'Trypanosomatids' in PubMed

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Search kinetoplastids OR kinetoplastid OR Kinetoplastida OR "trypanosoma brucei" OR leishmania OR brucei OR leishmaniasis OR "African trypanosomiasis"
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PubMed Results
Items 1 -6 of 6

1: Mol Biochem Parasitol. 2009 Apr 11. [Epub ahead of print]Click here to read

Functional characterization of stage-specific aminotransferases from trypanosomatids.

Marciano D, Maugeri DA, Cazzulo JJ, Nowicki C.

Instituto de Química y Fisicoquímica Biológica IQUIFIB-CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.

As part of a study on aminotransferases, genes coding for putative enzymes from Trypanosoma brucei and Leishmania major (alanine aminotransferases: ALATs, Tb927.1.3950 and LmjF12.0630; kynurenine aminotransferase: KAT, Tb10.389.1810; and tyrosine aminotransferase: TAT, LmjF36.2360) were cloned and functionally expressed in Escherichia coli. The putative T. brucei KAT, in fact coded for a glutamine aminotransferase (GlnAT), which exhibited a notably high affinity (in the mumolar range) towards glutamine and cysteine; in addition, like bacterial GlnATs and mammalian KATs, it was able to utilize different 2-oxoacids as amino acceptors. L. major TAT resembled T. cruzi TAT in substrate specificity, although the leishmanial enzyme did not exhibit ALAT activity. On the other hand, T. brucei ALAT, shortened by the first 65 amino acids assigned in the data bases, was functional and actively transaminated the substrate pair l-alanine and 2-oxoglutarate. Moreover in Western blots, the molecular size of the protein detected in crude extracts of T. brucei procyclics was identical to the value of the recombinant enzyme. Like T. brucei and T. cruzi orthologues, L. major ALAT displayed narrow substrate specificity. The leishmanial ALAT, like the T. cruzi enzyme, exhibited a dual subcellular localization, in the cytosol and in the mitochondrion. In line with the findings of comparative proteomic analyses of insect and mammalian stages of T. brucei and Leishmania parasites, our results also showed that T. cruzi ALAT is constitutively expressed, with remarkably higher levels being detected in amastigotes than in epimastigotes. ALATs are expressed in the clinically important stages of TriTryps, probably fulfilling an essential role, which deserves further studies.

PMID: 19443056 [PubMed - as supplied by publisher]

2: Parasitol Int. 2009 May 11. [Epub ahead of print]Click here to read

Purification and biochemical characterization of lysosomal acid phosphatases (EC 3.1.3.2) from blood stream forms, Trypanosoma brucei brucei.

Amlabu E, Nok AJ, Sallau AB.

Department of Biochemistry, Ahmadu Bello University, Zaria- Nigeria.

Three Acid phosphatases (ACP) were isolated and characterized from the lysosomes of blood stream forms of Trypanosoma brucei by a combination of isopynic and differential centrifugation through Ficoll, organic solvent precipitation, ion exchange on DEAE-cellulose 52 and size exclusion chromatography on Sephadex G-75 columns. The purified ACP emerged as three distinct peaks (ACP-P(1), ACP-P(2) and ACP-P(3)) with high specific activities and they moved homogenously on 12% SDS-PAGE each as a single band with relative molecular weight of 36 kDa, 25 kDa and 45 kDa respectively. The purified enzymes were active at an optimum pH and temperature of 5.5 and 40 degrees C respectively. The enzyme activities appeared to be ACP because their activities were enhanced at low pH values and inhibited by the acid phosphatase inhibitor, sodium flouride. ACP-P(1) and ACP-P(2) were sensitive to L-tartrate while ACP-P(3) was insensitive to L-tartrate. The kinetic analysis of the purified enzyme (ACP-P(1), ACP-P(2) and ACP-P(3)) determined using Para-nitrophenylphosphate as substrate gave K(M) values of 0.2 mM, 0.15 mM and 0.5 mM. Monofunctional group sulfhydryl group inhibitors; HgCl(2), and AgCl(2) strongly inhibited the activity of ACP-P(3) and millimolar concentrations of dithiothreitol and iodoacetamide activated and inhibited the activity of the ACP-P(3) respectively, suggesting the involvement of thiol groups at the active site of the enzyme. Thus, differentiating it from ACP-P(1) and ACP-P(2). The implication of these findings in relation to the pathology of trypanosomosis is discussed.

PMID: 19442761 [PubMed - as supplied by publisher]

3: Genomics. 2009 Jun;93(6):551-64. Epub 2009 Feb 10.Click here to read

Genome-wide analysis reveals increased levels of transcripts related with infectivity in peanut lectin non-agglutinated promastigotes of Leishmania infantum.

Alcolea PJ, Alonso A, Sánchez-Gorostiaga A, Moreno-Paz M, Gómez MJ, Ramos I, Parro V, Larraga V.

Departamento de Ciencia de Proteínas and Departamento de Microbiología Molecular, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CSIC), calle Ramiro de Maeztu, 9, 28040, Madrid, Spain.

Metacyclic promastigotes are transmitted during bloodmeals after development inside the gut of the sandfly vector. The isolation from axenic cultures of procyclic and metacyclic promastigotes by peanut lectin agglutination followed by differential centrifugation is controversial in Leishmania infantum. The purpose of this study has been to isolate both fractions simultaneously from the same population in stationary phase of axenic culture and compare their expression profiles by whole-genome shotgun DNA microarrays. The 317 genes found with meaningful values of stage-specific regulation demonstrate that negative selection of metacyclic promastigotes by PNA agglutination is feasible in L. infantum and both fractions can be isolated. This subpopulation up-regulates a cysteine peptidase A and several genes involved in lipophosphoglycan, proteophosphoglycan and glycoprotein biosynthesis, all related with infectivity. In fact, we have confirmed the increased infection rate of PNA(-) promastigotes by U937 human cell line infection experiments. These data support that metacyclic promastigotes are related with infectivity and the lack of agglutination with PNA is a phenotypic marker for this subpopulation.

PMID: 19442635 [PubMed - in process]

4: Curr Drug Metab. 2009 Mar;10(3):247-55.

Cellular transport and lipid interactions of miltefosine.

Barratt G, Saint-Pierre-Chazalet M, Loiseau PM.

CNRS UMR 8612, 5 rue J.B. Clément, 92296 CHATENAY-MALABRY, France. gillian.barratt@u-psud.fr.

Miltefosine (hexadecylphosphocholine, HePC) is an alkyl phospholipid which was first developed as an anticancer agent for local treatment of skin metastases. It was later found to have remarkable activity against Leishmania parasites by the oral route and is marketed as Impavido(R) for this indication. The mechanism of action of HePC involves interaction with lipids and in particular membrane lipids - phospholipids and sterols. Studies of interactions between HePC and these lipids carried out in model systems suggest an affinity of HePC for cholesterol-rich lipid rafts. The uptake of HePC by cancer cells begins by insertion into the plasma membrane which may be followed by internalization. Within the plasma membrane, HePC interferes with the functioning of a number of enzymes involved in phospholipid metabolism, including protein kinase C and the phospholipases A(2), C and D, and can also induce apoptosis. Effects on lipid metabolism have also been observed in Leishmania parasites. In these organisms, a proposed mechanism of HePC uptake can be proposed: HePC inserts into the outer leaflet of the plasma membrane as monomers when its concentration is below the critical micellar concentration (CMC) and as both monomers and oligomers when it is above the CMC. Thereafter, a two-subunit aminophospholipid translocase, LdMT-LdRos3, internalizes the drug. Some evidence obtained in the Caco-2 intestinal cell model suggests that a similar process may occur during the oral absorption of HePC. Finally, the use of phospholipid vesicles (liposomes) as carrier systems for HePC, reducing its toxic side-effects, is reviewed.

PMID: 19442087 [PubMed - in process]

5: Biochem Biophys Res Commun. 2009 May 8;382(3):626-30. Epub 2009 Mar 19.Click here to read LinkOut

Different catalytic properties of two highly homologous triosephosphate isomerase monomers.

Zárate-Pérez F, Chánez-Cárdenas ME, Arreola R, Torres-Larios A, Vázquez-Contreras E.

Instituto de Química, Departamento de Bioquímica, Universidad Nacional Autónoma de Mexico, Circuito Exterior, Mexico, DF 04510, Mexico.

It is assumed that amino acid sequence differences in highly homologous enzymes would be found at the peripheral level, subtle changes that would not necessarily affect catalysis. Here, we demonstrate that, using the same set of mutations at the level of the interface loop 3, the activity of a triosephosphate isomerase monomeric enzyme is ten times higher than that of a homologous enzyme with 74% identity and 86% similarity, whereas the activity of the native, dimeric enzymes is essentially the same. This is an example of how the dimeric biological unit evolved to compensate for the intrinsic differences found at the monomeric species level. Biophysical techniques of size exclusion chromatography, dynamic light scattering, X-ray crystallography, fluorescence and circular dichroism, as well as denaturation/renaturation assays with guanidinium hydrochloride and ANS binding, allowed us to fully characterize the properties of the new monomer.

PMID: 19303397 [PubMed - indexed for MEDLINE]

6: Braz J Infect Dis. 2008 Dec;12(6):480-2.Click here to read LinkOut

Anti-Trypanosoma cruzi antibody detection in blood donors in the Southern Brazil.

Araújo AB, Vianna EE, Berne ME.

Department of Microbiology and Parasitology, Federal University of Pelotas, Pelotas, RS, Brazil. anelise_araujo@yahoo.com.br

Trypanosoma cruzi, the causal agent of Chagas' Disease, is a widely spread protozoa in America. Blood transfusion is the secondly most important way of acquiring the infection. In blood banks, tests are performed to eliminate potentially infected blood. This study aimed to evaluate the positivity for T. cruzi in blood samples of donor's candidates in Southern Brazil. The study was based on a sampling containing all blood donors of Hemopel - a Pelotas City Blood Center, Rio Grande do Sul State, Brazil, from 2004 to 2005. Serological study was performed using ELISA Chagatest. Sampling containing values +/- 20% cut off were evaluated using ELISA Chagatek, ELISA Alka/Adaltis, IHA Chagatest and IIF Imunocruzi. TESA-Blot was used as a confirmatory procedure in situations where blood samples showed conflicting results. From 4,482 samples collected in 2004 and 2005, the reactivity for anti-T. cruzi was 0.96% (43). Among those, 21 cases (0.47%) were confirmed as positive - most of them were female, with low school level and averaging 47.2% years old. Interestingly, the blood donors are not aware of being contaminated and this fact makes it difficult for controlling the disease. Chagas' Disease was one of the main reasons for discarding blood bags through serological control in Southern Brazil. Sampling reactivity showed variation among the different techniques used for anti-T. cruzi research. In order to obtaining more secure and conclusive results, more than one diagnostic technique must be used.

PMID: 19287834 [PubMed - indexed for MEDLINE]

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