Descripción: 1. 1. The sensitivity of partially purified low Km, phosphodiesterase (PDE) from Mucor rouxii to pharmacological agents and cAMP analogs was studied. The IC50 obtained were compared with those reported for PDEs from higher eukaryotes. 2. 2. The best inhibitors of the hydrolysis of 1 gmM cAMP were SQ 65.442 (IC50, c 10 μM), dipyridamol and CI 930. cGMP was not an inhibitor (IC50 > 1000 μm). 3. 3. The cAMP analogs were tested as inhibitors of the hydrolysis of 0. l μM cAMP. 8-Aminohexylamino cAMP was the best inhibitor with an IC50 of c 1 μM. 4. 4. A sedimentation profile of Mucor PDE was assayed in the presence of several pharmacological inhibitors and eAMP analogs. No isoforms with different sensitivity towards the inhibitors were detected. Forms with slightly different behaviour towards some cAMP analogs were observed. © 1990.

Descripción: Previous work showed that two different strains derived from a culture of Rhizobium meliloti 102F51 differed with respect to phage specificity, agglutinability by alfalfa seed lectin, and synthesis of a galactose-containing polysaccharide (R.A. Ugalde, J. Handelsman, and W.J. Brill, J. Bacteriol. 166:148-154, 1986). Inner membranes from the more competitive strain incorporated glactose from UDP-galactose when a thermostable factor was present. This factor has now been identified as UDP-galacturonic acid. UDP-glucuronic acid was also active as a donor; however, this activity may be due to the presence of a 4-epimerase. Galacturonic acid, together with galactose, is incorporated into the reaction product, which appears to be a polysaccharide formed by several repeating units of these two monosaccharides. Partial acid hydrolysis liberates the disaccharide with galactose at the reducing end.

Descripción: Background/ Aims: Since the reversible phosphorylation of tyrosyl residues is a critical event in cellular signaling pathways activated by erythropoietin (Epo), attention has been focused on protein tyrosine phosphatases (PTPs) and their coordinated action with protein tyrosine kinases. The prototypic member of the PTP family is PTP1B, a widely expressed non-receptor PTP located both in cytosol and intracellular membranes via its hydrophobic C-terminal targeting sequence. PTP1B has been implicated in the regulation of signaling pathways involving tyrosine phosphorylation induced by growth factors, cytokines, and hormones, such as the downregulation of erythropoietin and insulin receptors. However, little is known about which factor modulates the activity of this enzyme. Methods: The effect of Epo on PTP1B expression was studied in the UT-7 Epo-dependent cell line. PTP1B expression was analyzed under different conditions by Real-Time PCR and Western blot, while PTP1B phosphatase activity was determined by a p-nitrophenylphosphate hydrolysis assay. Results: Epo rapidly induced an increased expression of PTP1B which was associated with higher PTP1B tyrosine phosphorylation and phosphatase activity. The action of Epo on PTP1B induction involved Janus Kinase 2 (JAK2) and Phosphatidylinositol-3 kinase (PI3K). Conclusion: The results allow us to suggest for the first time that, besides modulating Epo/Epo receptor signaling, PTP1B undergoes feedback regulation by Epo. Copyright © 2007 S. Karger AG.

Descripción: The lipopeptidophosphoglycan from Trypanosoma cruzi is a glycosylated inositol‐phosphoceramide isolated from epimastigotes at the stationary phase of growth (4–5 days). We have now purified two similar glycoinositolphospholipids (glycoinositolphospholipid A and glycoinositolphospholipid B) from epimastigotes after the second day of culture growth. [3H]Palmitic acid was incorporated into 1‐O‐hexadecyl‐2‐O‐palmitoylglycerol in glycoinositolphospholipid A and into ceramide in glycoinositolphospholipid B. The lipids were released by incubation with glycosylphosphatidylinositol‐specific phospholipase C from Bacillus thuringiensis or by chemical methods. After alkaline hydrolysis, the lipids were analysed by GLC/MS. In glycoinositolphospholipid A the resulting lipids corresponded to 1‐O‐hexadecylglycerol and palmitic acid. The ceramide components in glycoinositolphospholipid B are sphinganine, palmitic acid and lignoceric acid. The oligosaccharides could be degraded by nitrous acid and further enzymic treatment showed that the two glycoinositolphospholipids isolated from T. cruzi share the common core structure of the glycosylphosphatidylinositol membrane anchors. The microheterogeneity was determined, as well as the substitution by galactose, and was mainly in the furanose configuration as was previously described for lipopeptidophosphoglycan. However, methylation analysis indicated that 20% of the galactose is in the pyranose from. Both glycoinositolphospholipids mainly differ in the lipid moiety. Copyright © 1993, Wiley Blackwell. All rights reserved

Descripción: A psychrotolerant marine bacterial strain, designated JUB59 T, was isolated from Antarctic surface seawater and classified as a new species of the genus Bizionia. Here, we present the first draft genome sequence for this genus, which suggests interesting features such as UV resistance, hydrolytic exoenzymes, and nitrogen metabolism. © 2011, American Society for Microbiology.

Descripción: Aims: To study the modification of the cell wall of Lactobacillus casei ATCC 393 grown in high salt conditions. Methods and Results: Differences in the overall structure of cell wall between growth in high salt (MRS + 1 mol l -1 NaCl; N condition) and control (MRS; C condition) conditions were determined by transmission electronic microscopy and analytical procedures. Lactobacillus casei cells grown in N condition were significantly larger than cells grown under unstressed C condition. Increased sensitivity to mutanolysin and antibiotics with target in the cell wall was observed in N condition. Purified cell wall also showed the increased sensitivity to lysis by mutanolysin. Analysis of peptidoglycan (PG) from stressed cells showed that modification was at the structural level in accordance with a decreased PG cross-link involving penicillin-binding proteins (PBP). Nine PBP were first described in this species and these proteins were expressed in low percentages or presented a modified pattern of saturation with penicillin G (Pen G) during growth in high salt. Three of the essential PBP were fully saturated in N condition at lower Pen G concentrations than in C condition, suggesting differences in functionality in vivo. Conclusions: The results show that growth in high salt modified the structural properties of the cell wall. Significance and Impact of Study: Advances in understanding the adaptation to high osmolarity, in particular those involving sensitivity to lysis of lactic acid bacteria.

Descripción: β-Lapachone, an o-naphthoquinone, induces a novel caspase- and p53-independent apoptotic pathway dependent on NAD (P) H:quinone oxidoreductase 1 (NQO1). NQO1 reduces β-lapachone to an unstable hydroquinone that rapidly undergoes a two-step oxidation back to the parent compound, perpetuating a futile redox cycle. A deficiency or inhibition of NQO1 rendered cells resistant to beta;-lapachone. Thus, β-lapachone has great potential for the treatment of specific cancers with elevated NQO1 levels (e.g., breast, non - small cell lung, pancreatic, colon, and prostate cancers). We report the development of mono(arylimino) derivatives of β-lapachone as potential prodrugs. These derivatives are relatively nontoxic and not substrates for NQO1 when initially diluted in water. In solution, however, they undergo hydrolytic conversion to β-lapachone at rates dependent on the electron-withdrawing strength of their substituent groups and pH of the diluent. NQO1 enzyme assays, UV-visible spectrophotometry, high-performance liquid chromatography-electrospray ionization-mass spectrometry, and nuclear magnetic resonance analyses confirmed and monitored conversion of each derivative to β-lapachone. Once converted, β-lapachone derivatives caused NQO1-dependent, μ-calpain-mediated cell death in human cancer cells identical to that caused by β-lapachone. Interestingly, coadministration of N-acetyt-L-cysteine prevented derivative-induced cytotoxicity but did not affect β-lapachone lethality. Nuclear magnetic resonance analyses indicated that prevention of β-lapachone derivative cytotoxicity was the result of direct modification of these derivatives by N-acetyl-L-cysteine, preventing their conversion to β-lapachone. The use of β-lapachone mono(arylimino) prodrug derivatives, or more specifically a derivative converted in a tumor-specific manner (i.e., in the acidic local environment of the tumor tissue), should reduce normal tissue toxicity while eliciting tumor-selective cell killing by NQO1 bioactivation. © 2005 American Association for Cancer Research.