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Cystathionine β-synthase (CBS) is a homocysteine metabolizing enzyme that contains pyridoxal phosphate (PLP) and a six-coordinate heme cofactor of unknown function. CBS was inactivated by peroxynitrite, the product of nitric oxide and superoxide radicals. The IC50 was ~150 μM for 5 μM ferric CBS. Stopped-flow kinetics and competition experiments showed a direct reaction with a second-order rate constant of (2.4–5.0) × 104 M−1 s−1 (pH 7.4, 37 °C). The radicals derived from peroxynitrite, nitrogen dioxide and carbonate radical, also inactivated CBS. Exposure to peroxynitrite did not modify bound PLP but led to nitration of Trp208, Trp43 and Tyr223 and alterations in the heme environment including loss of thiolate coordination, conversion to high spin and bleaching, with no detectable formation of oxo-ferryl compounds nor promotion of one-electron processes. This study demonstrates the susceptibility of CBS to reactive oxygen/nitrogen species, with potential relevance to hyperhomocysteinemia, a risk factor for cardiovascular diseases.

This exercise is intended to introduce undergraduate biochemistry students to the analysis of antioxidants as a biotechnological tool. In addition, some statistical resources will also be used and discussed. Antioxidants play an important metabolic role, preventing oxidative stress-mediated cell and tissue injury. Knowing the antioxidant content of nutritional components can help make informed decisions about diet design, and increase the commercial value of antioxidant-rich natural products. As a reliable and convenient technique to evaluate the whole spectrum of antioxidants present in biological samples is lacking, the general consensus is to use more than one technique. We have chosen two widely used and inexpensive methods, Trolox-equivalent antioxidant capacity and the ferric reducing antioxidant power assays, to evaluate the antioxidant content of several fruits, and to compare and analyze the correlation between both assays.

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Abstract:The current pharmacological Chagas disease treatments, using Nifurtimox or Benznidazole, show limited therapeutic results and are associated with potential side effects, OPEN ACCESSMolecules 2015, 20 14596 like mutagenicity. Using random screening we have identified new chemotypes that were able to inhibit relevant targets of the Trypanosoma cruzi. We found 3H-[1,2]dithioles with the ability to inhibit Trypanosoma cruzi triosephosphate isomerase (TcTIM). Herein, we studied the structural modifications of this chemotype to analyze the influence of volume, lipophilicity and electronic properties in the anti-T. cruzi activity. Their selectivity to parasites vs. mammalian cells was also examined. To get insights into a possible mechanism of action, the inhibition of the enzymatic activity of TcTIM and cruzipain, using the isolated enzymes, and the inhibition of membrane sterol biosynthesis and excreted metabolites, using the whole parasite, were achieved. We found that this structural framework is interesting for the generation of innovative drugs for the treatment of Chagas disease.