Microcins are a family of low-molecular weight bacteriocins produced and secreted by Gram-negative bacteria. This review is focused on microcin E492, a pore-forming bacteriocin produced by Klebsiella pneumoniae RYC492 that exerts its antibacterial action on related strains. The steps necessary for the production of active microcin E492 involve post-translational modification with a catechol-type siderophore at the C-terminal and proteolytic processing during export to the extracellular space. This bacteriocin has a modular structure, with a toxic domain at the N-terminal and an uptake domain at the C-terminal of the mature protein. The mechanism by which the C-terminal of microcin E492 is recognized by catecholate siderophore receptors is called the "Trojan horse" strategy, because the C-terminal structure mimics essential bacterial elements, which are recognized by the respective receptors and translocated across the outer membrane to exert antibacterial action. The C-terminal uptake module can be exchanged and used with other toxic domains. Microcin E492 also has a cytotoxic effect on malignant human cell lines. The cytotoxic mechanism is through apoptosis, a desired mechanism for cancer therapy. The ability of microcin E492 to form amyloid-like fibrils constitutes a property that can be exploited in the formulation of this bacteriocin as an antitumoral agent, because these fibrils can behave as stable depots to ensure the sustained release of a biologically active molecule. Alternatively, live bacteria can be used as a continuous source of microcin E492 production in specific tumors.
Objective:To determine the level of agreement between the American (Chilean) and British food composition tables in estimating intakes of macronutrients and antioxidants. Design, setting and subjects: Information based on a food-frequency questionnaire with emphasis on antioxidants was collected from 95 Chileans aged 24-28 years. Nutritional composition was analysed using the British table of food composition and the American table of food composition modified by Chilean food items. Mean differences and limits of agreement (LOAs) of estimated intake were assessed. Results: Mean differences between the two tables of food composition ranged from 5.3% to 8.9% higher estimates when using the American (Chilean) table for macronutrients. For micronutrients, a bias towards a higher mean was observed for vitamin E, iron and magnesium when the American (Chilean) table was used, but the opposite was observed for vitamin A and selenium. The intra-class correlation coefficient (ICC) ranged from 0.86 (95% confidence interval (CI) 0.81 -0.91) to 0.998 (95% CI 0.995 -1.00), indicating high to excellent agreement. LOAs for macronutrients and vitamins A and C were satisfactory, as they were sufficiently narrow. There was more uncertainty for other micronutrients. Conclusion: The American table gives relative overestimates of macronutrients in comparison to the British table, but the relative biases for micronutrients are inconsistent. Estimates of agreement between the two food composition tables provide reassurance that results are interchangeable for the majority of nutrients.
The fatty acid composition of the oils of five varieties of winged beans,Psophocarpus tetragonolobus (L.) DC, was determined and found to be similar to peanut oil. The total unsaturated fatty acids ranged from 53.8% to 68.5% (mean, 62.0%). Oleic acid and linoleic acids were the major unsaturated fatty acids. The major saturated fatty acids were behenic, palmitic and stearic acids. Parinaric acid, a toxic fatty acid, previously reported to occur in winged beans, was not present in the oil of the winged beans analyzed.
The proximate composition was determined for the mature seeds of five varieties of winged beans, Psophocarpus tetragonolobus (L.) DC. The results showed that the varieties analyzed had a high protein and fat content, which was similar to soybeans. The protein content (mean * standard deviation) of the five varieties as received was 36.0 * 1.8%, the fat content, 15.2 & 1.2% and the moisture content 10.4 -+ 1.5%. The endosperm in winged bean variety TPT-2 was found to constitute 84% of the dry weight of the seeds, the hulls about 16%. Whole beans as received contain about 14% 'dietary fibre' measured as neutral detergent fibre. The dietary fibre is concentrated in the hulls.
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