DSpace Angular :: Browsing by Author "Fuentes Lemus, Eduardo Felipe"

Browsing by Author "Fuentes Lemus, Eduardo Felipe"

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Binding of rose bengal to lysozyme modulates photooxidation and cross-linking reactions involving tyrosine and tryptophan
(2019) Fuentes Lemus, Eduardo Felipe; Mariotti, Michele; Hägglund, Per; Leinisch, Fabian; Fierro Huerta, Angélica; Silva, Eduardo; López Alarcón, Camilo Ignacio; Davies, Michael J.
Crowding modulates the glycation of plasma proteins: In vitro analysis of structural modifications to albumin and transferrin and identification of sites of modification
(2022) Fuentes Lemus, Eduardo Felipe; Reyes Valenzuela, Juan Sebastián; López Alarcón, Camilo Ignacio; Davies, Michael J.
Protein modification occurs in biological milieus that are characterized by high concentrations of (macro)mol-ecules (i.e. heterogeneous and packed environments). Recent data indicate that crowding can modulate the extent and rate of protein oxidation, however its effect on other post-translational modifications remains to be explored. In this work we hypothesized that crowding would affect the glycation of plasma proteins. Physiologically-relevant concentrations of albumin (35 mg mL-1) and transferrin (2 mg mL-1) were incubated with methylglyoxal and glyoxal (5 mu M-5 mM), two alpha-oxoaldehyde metabolites that are elevated in the plasma of people with diabetes. Crowding was induced by adding dextran or ficoll polymers. Electrophoresis, electron microscopy, fluorescence spectroscopy and mass spectrometry were employed to investigate the structural consequences of glycation under crowded conditions. Our data demonstrate that crowding modulates the extent of formation of transferrin cross-links, and also the modification pathways in both albumin and transferrin. Arginine was the most susceptible residue to modification, with lysine and cysteine also affected. Loss of 0.48 and 7.28 arginine residues per protein molecule were determined on incubation with 500 mu M methylglyoxal for albumin and transferrin, respectively. Crowding did not influence the extent of loss of arginine and lysine for either protein, but the sites of modification, detected by LC-MS, were different between dilute and crowded conditions. These data confirm the relevance of studying modification processes under conditions that closely mimic biological milieus. These data unveil additional factors that influence the pattern and extent of protein modification, and their structural consequences, in biological systems.
Effect of macromolecular crowding on protein oxidation: Consequences on the rate, extent and oxidation pathways
(2021) Fuentes Lemus, Eduardo Felipe; Reyes Valenzuela, Juan Sebastián; Gamon, Luke F.; López Alarcón, Camilo Ignacio; Davies, Michael J.
Biological systems are heterogeneous and crowded environments. Such packed milieus are expected to modulate reactions both inside and outside the cell, including protein oxidation. In this work, we explored the effect of macromolecular crowding on the rate and extent of oxidation of Trp and Tyr, in free amino acids, peptides and proteins. These species were chosen as they are readily oxidized and contribute to damage propagation. Dextran was employed as an inert crowding agent, as this polymer decreases the fraction of volume available to other (macro)molecules. Kinetic analysis demonstrated that dextran enhanced the rate of oxidation of free Trp, and peptide Trp, elicited by AAPH-derived peroxyl radicals. For free Trp, the rates of oxidation were 15.0 ± 2.1 and 30.5 ± 3.4 μM min−1 without and with dextran (60 mg mL−1) respectively. Significant increases were also detected for peptide-incorporated Trp. Dextran increased the extent of Trp consumption (up to 2-fold) and induced short chain reactions. In contrast, Tyr oxidation was not affected by the presence of dextran. Studies on proteins, using SDS-PAGE and LC-MS, indicated that oxidation was also affected by crowding, with enhanced amino acid loss (45% for casein), chain reactions and altered extents of oligomer formation. The overall effects of dextran-mediated crowding were however dependent on the protein structure. Overall, these data indicate that molecular crowding, as commonly encountered in biological systems affect the rates, and extents of oxidation, and particularly of Trp residues, illustrating the importance of appropriate choice of in vitro systems to study biological oxidations.
Evaluation of the antioxidant capacity of food samples: a chemical examination of the oxygen radical absorbance capacity assay
(WILEY-BLACKWELL, 2018) Dorta Pérez, Eva; Fuentes Lemus, Eduardo Felipe; Speisky, Hernan; Lissi Gervaso, Eduardo A.; López Alarcón, Camilo Ignacio; Apak, Resat; Capanoglu, Esra; Shahidi, Fereidoon
This chapter describes, from a critical point of view, the main in vitro methodologies employed to assess the antioxidant capacity (AC) of food samples. Considering the wide use of the oxygen radical absorbance capacity (ORAC) assay, it presents a chemical examination of this methodology. The methods for AC evaluation are based on different strategies; these include the use of colored and stable free radicals, evaluation of the capacity of antioxidants to reduce cupric or ferric ions, estimation of the ability of phenolic compounds (PC) to protect a target molecule exposed to a free radical source, and evaluation of the capacity of PC to form nanoparticles. When the antioxidant activity of a particular sample is evaluated, it is recommended to know the meanings and limitations of the assays being employed. In the case of the ORAC assay, the nature of the free radicals generated during the thermolysis of AAPH should also be considered.
Formation and characterization of crosslinks, including Tyr-Trp species, on one electron oxidation of free Tyr and Trp residues by carbonate radical anion
(2020) Figueroa Alegría, Juan David; Zarate Méndez, Ana María; Fuentes Lemus, Eduardo Felipe; Davies, M. J.; Lopez Alarcon Camilo Ignacio
Dityrosine and ditryptophan bonds have been implied in protein crosslinking. This is associated with oxidative stress conditions including those involved in neurodegenerative pathologies and age-related processes. Formation of dityrosine and ditryptophan derives from radical-radical reactions involving Tyr(center dot) and Trp(center dot) radicals. However, cross reactions of Tyr(center dot) and Trp(center dot) leading to Tyr-Trp crosslinks and their biological consequences have been less explored. In the present work we hypothesized that exposure of free Tyr and Trp to a high concentration of carbonate anion radicals (CO3 center dot-), under anaerobic conditions, would result in the formation of Tyr-Trp species, as well as dityrosine and ditryptophan crosslinks. Here we report a simple experimental procedure, employing CO3 center dot- generated photochemically by illumination of a Co(iii) complex at 254 nm, that produces micromolar concentrations of Tyr-Trp crosslinks. Analysis by mass spectrometry of solutions containing only the individual amino acids, and the Co(iii) complex, provided evidence for the formation ofo,o '-dityrosine and isodityrosine from Tyr, and three ditryptophan dimers from Trp. When mixtures of Tyr and Trp were illuminated in an identical manner, Tyr-Trp crosslinks were detected together with dityrosine and ditryptophan dimers. These results indicate that there is a balance between the formation of these three classes of crosslinks, which is dependent on the Tyr and Trp concentrations. The methods reported here allow the generation of significant yields of isolated Tyr-Trp adducts and their characterization. This technology should facilitate the detection, and examination of the biological consequences of Tyr-Trp crosslink formation in complex systems in future investigations.
Free radicals derived from gamma-radiolysis of water and AAPH thermolysis mediate oxidative crosslinking of eGFP involving Tyr-Tyr and Tyr-Cys bonds : the fluorescence of the protein is conserved only towards peroxyl radicals
(2020) Zamora Jofré, Renato Andrés; Fuentes Lemus, Eduardo Felipe; Barrias, P.; Herrera-Morande, A.; Mura, F.; Guixe, V.; Castro-Fernandez, V.; Rojas, T.; López Alarcón, Camilo Ignacio; Aguirre, P.; Rivas-Aravena, A.; Aspee, A.
Implications of differential peroxyl radical-induced inactivation of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase for the pentose phosphate pathway
(Nature Research, 2022) Reyes Valenzuela, Juan Sebastián; Figueroa Alegría, Juan David; Martínez Rojas, Francisco Javier; López Alarcon, Camilo Ignacio; Fuentes Lemus, Eduardo Felipe; Hagglund, P.M.; Davies, Michael J.; Fierro Huerta, Angelica María; Arenas, Felipe
© 2022, The Author(s).Escherichia coli glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) are key enzymes of the pentose phosphate pathway, responsible for the NADPH production in cells. We investigated modification of both enzymes mediated by peroxyl radicals (ROO·) to determine their respective susceptibilities to and mechanisms of oxidation. G6PDH and 6PGDH were incubated with AAPH (2,2?-azobis(2-methylpropionamidine)dihydrochloride), which was employed as ROO· source. The enzymatic activities of both enzymes were determined by NADPH release, with oxidative modifications examined by electrophoresis and liquid chromatography (LC) with fluorescence and mass (MS) detection. The activity of G6PDH decreased up to 62.0 ± 15.0% after 180 min incubation with 100 mM AAPH, whilst almost total inactivation of 6PGDH was determined under the same conditions. Although both proteins contain abundant Tyr (particularly 6PGDH), these residues were minimally affected by ROO·, with Trp and Met being major targets. LC–MS and in silico analysis showed that the modification sites of G6PDH are distant to the active site, consistent with a dispersed distribution of modifications, and inactivation resulting from oxidation of multiple Trp and Met residues. In contrast, the sites of oxidation detected on 6PGDH are located close to its catalytic site indicating a more localized oxidation, and a consequent high susceptibility to ROO·-mediated inactivation.
Oxidation of free, peptide and protein tryptophan residues mediated by AAPH-derived free radicals: role of alkoxyl and peroxyl radicals
(2016) Fuentes Lemus, Eduardo Felipe; Dorta Pérez, Eva; Escobar Álvarez, Elizabeth; Aspée, A.; Pino, E.; Abasq, M. L.; Speisky, Hernán; Silva, E.; Lissi, E.; Davies, M. J.; López Alarcón, Camilo Ignacio
Oxidation of lysozyme induced by peroxyl radicals involves amino acid modifications, loss of activity, and formation of specific crosslinks
(2021) Fuentes Lemus, Eduardo Felipe; Mariotti, Michele; Hägglund, Per; Leinisch, Fabian; Fierro Huerta, Angélica; Silva Stevens, Eduardo Andrés; Davies, Michael J.; López Alarcón, Camilo Ignacio
The present work examined the oxidation and crosslinking of the anti-bacterial enzyme lysozyme (Lyso), which is present in multiple biological fluids, and released from the cytoplasmic granules of macrophages and neutrophils at sites of infection and inflammation. It is therefore widely exposed to oxidants including peroxyl radicals (ROO?). We hypothesized that exposure to ROO? would generate specific modifications and inter- and intraprotein crosslinks via radical-radical reactions. Lyso was incubated with AAPH (2,2?-azobis(2-methylpropionamidine) dihydrochloride) as a ROO? source. Enzymatic activity was assessed, while oxidative modifications were detected and quantified using electrophoresis and liquid chromatography (UPLC) with fluorescence or mass detection (MS). Computational models of AAPH-Lyso interactions were developed. Exposure of Lyso to AAPH (10 and 100 mM for 3 h, and 20 mM for 1 h), at 37 ?C, decreased enzymatic activity. 20 mM AAPH showed the highest efficiency of Lyso inactivation (1.78 mol of Lyso inactivated per ROO?). Conversion of Met to its sulfoxide, and to a lesser extent, Tyr oxidation to 3,4-dihydroxyphenylalanine and diTyr, were detected by UPLCMS. Extensive transformation of Trp, involving short chain reactions, to kynurenine, oxindole, hydroxytryptophan, hydroperoxides or di-alcohols, and N-formyl-kynurenine was detected, with Trp62, Trp63 and Trp108 the most affected residues. Interactions of AAPH inside the negatively-charged catalytic pocket of Lyso, with Trp108, Asp52, and Glu35, suggest that Trp108 oxidation mediates, at least partly, Lyso inactivation. Crosslinks between Tyr20-Tyr23 (intra-molecular), and Trp62-Tyr23 (inter-molecular), were detected with both proximity (Tyr20-Tyr23), and chain flexibility (Trp62) appearing to favor the formation of covalent crosslinks.
Oxidation of myofibrillar proteins induced by peroxyl radicals : role of oxidizable amino acids
(2019) Dorta Pérez, Eva; Avila, F.; Fuentes Lemus, Eduardo Felipe; Fuentealba Patiño, Denis Alberto; López Alarcón, Camilo Ignacio
Oxidative Crosslinking of Peptides and Proteins: Mechanisms of Formation, Detection, Characterization and Quantification
(2022) Fuentes Lemus, Eduardo Felipe; Hägglund, Per; López Alarcón, Camilo Ignacio; Davies, Michael J.
Covalent crosslinks within or between proteins play a key role in determining the structure and function of proteins. Some of these are formed intentionally by either enzymatic or molecular reactions and are critical to normal physiological function. Others are generated as a consequence of exposure to oxidants (radicals, excited states or two-electron species) and other endogenous or external stimuli, or as a result of the actions of a number of enzymes (e.g., oxidases and peroxidases). Increasing evidence indicates that the accumulation of unwanted crosslinks, as is seen in ageing and multiple pathologies, has adverse effects on biological function. In this article, we review the spectrum of crosslinks, both reducible and non-reducible, currently known to be formed on proteins; the mechanisms of their formation; and experimental approaches to the detection, identification and characterization of these species.
Quantification of carbonate radical formation by the bicarbonate-dependent peroxidase activity of superoxide dismutase 1 using pyrogallol red bleaching
(2019) Figueroa Alegría, Juan David; Fuentes Lemus, Eduardo Felipe; Dorta Pérez, Eva; Melin, Victoria; Cortés Ríos, Javiera Alejandra; Faúndez Cáceres, Mario; Contreras, David; Denicola, Ana; Álvarez, Beatriz; Davies, Michael J.; López Alarcón, Camilo Ignacio
Carbonate radicals (CO3radical dot-) are generated by the bicarbonate-dependent peroxidase activity of cytosolic superoxide dismutase (Cu,Zn-SOD, SOD-1). The present work explored the use of bleaching of pyrogallol red (PGR) dye to quantify the rate of CO3radical dot- formation from bovine and human SOD-1 (bSOD-1 and hSOD-1, respectively). This approach was compared to previously reported methods using electron paramagnetic resonance spin trapping with DMPO, and the oxidation of ABTS (2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid). The kinetics of PGR consumption elicited by CO3radical dot- was followed by visible spectrophotometry. Solutions containing PGR (5–200 μM), SOD-1 (0.3–3 μM), H2O2 (2 mM) in bicarbonate buffer (200 mM, pH 7.4) showed a rapid loss of the PGR absorption band centered at 540 nm. The initial consumption rate (Ri) gave values independent of the initial PGR concentration allowing an estimate to be made of the rate of CO3radical dot- release of 24.6 ± 4.3 μM min−1 for 3 μM bSOD-1. Both bSOD-1 and hSOD-1 showed a similar peroxidase activity, with enzymatic inactivation occurring over a period of 20 min. The single Trp residue (Trp32) present in hSOD-1 was rapidly consumed (initial consumption rate 1.2 ± 0.1 μM min−1) with this occurring more rapidly than hSOD-1 inactivation, suggesting that these processes are not directly related. Added free Trp was rapidly oxidized in competition with PGR. These data indicate that PGR reacts rapidly and efficiently with CO3radical dot- resulting from the peroxidase activity of SOD-1, and that PGR-bleaching is a simple, fast and cheap method to quantify CO3radical dot- release from bSOD-1 and hSOD-1 peroxidase activity.
Role of amino acid oxidation and protein unfolding in peroxyl radical and peroxynitrite-induced inactivation of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides
(2022) Figueroa Alegría, Juan David; Fuentes Lemus, Eduardo Felipe; Reyes Valenzuela, Juan Sebastián; Loaiza Hernández, Matías Ignacio; Aliaga Miranda, Margarita Elly; Fierro Huerta, Angélica; Leinisch, Fabian; Hagglund, Per; Davies, Michael J.; López Alarcón, Camilo Ignacio
The mechanisms underlying the inactivation of Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase (G6PDH) induced by peroxyl radicals (ROO center dot) and peroxynitrite (ONOO-), were explored. G6PDH was incubated with AAPH (2,2'-azobis(2-methylpropionamidine)dihydrochloride), used as ROO center dot source, and ONOO-. Enzymatic activity was assessed by NADPH generation, while oxidative modifications were analyzed by gel electrophoresis and liquid chromatography (LC) with fluorescence and mass detection. Changes in protein conformation were studied by circular dichroism (CD) and binding of the fluorescent dye ANS (1-anilinonaph-thalene-8-sulfonic acid). Incubation of G6PDH (54.4 mu M) with 60 mM AAPH showed an initial phase without significant changes in enzymatic activity, followed by a secondary time-dependent continuous decrease in activity to similar to 59% of the initial level after 90 min. ONOO- induced a significant and concentration-dependent loss of G6PDH activity with similar to 46% of the initial activity lost on treatment with 1.5 mM ONOO-. CD and ANS fluorescence indicated changes in G6PDH secondary structure with exposure of hydrophobic sites on exposure to ROO center dot, but not ONOO-. LC-MS analysis provided evidence for ONOO--mediated oxidation of Tyr, Met and Trp residues, with damage to critical Met and Tyr residues underlying enzyme inactivation, but without effects on the native (dimeric) state of the protein. In contrast, studies using chloramine T, a specific oxidant of Met, provided evidence that oxidation of specific Met and Trp residues and concomitant protein unfolding, loss of dimer structure and protein aggregation are involved in G6PDH inactivation by ROO center dot. These two oxidant systems therefore have markedly different effects on G6PDH structure and activity.
The enzymes of the oxidative phase of the pentose phosphate pathway as targets of reactive species: consequences for NADPH production
(2023) Fuentes Lemus, Eduardo Felipe; Reyes Valenzuela, Juan Sebastián; Figueroa Alegría, Juan David; Davies, Michael J.; López Alarcón, Camilo Ignacio
The pentose phosphate pathway (PPP) is a key metabolic pathway. The oxidative phase of this process involves three reactions catalyzed by glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconolactonase (6PGL) and 6-phosphogluconate dehydrogenase (6PGDH) enzymes. The first and third steps (catalyzed by G6PDH and 6PGDH, respectively) are responsible for generating reduced nicotinamide adenine dinucleotide phosphate (NAPDH), a key cofactor for maintaining the reducing power of cells and detoxification of both endogenous and exogenous oxidants and electrophiles. Despite the importance of these enzymes, little attention has been paid to the fact that these proteins are targets of oxidants. In response to oxidative stimuli metabolic pathways are modulated, with the PPP often up-regulated in order to enhance or maintain the reductive capacity of cells. Under such circumstances, oxidation and inactivation of the PPP enzymes could be detrimental. Damage to the PPP enzymes may result in a downward spiral, as depending on the extent and sites of modification, these alterations may result in a loss of enzymatic activity and therefore increased oxidative damage due to NADPH depletion. In recent years, it has become evident that the three enzymes of the oxidative phase of the PPP have different susceptibilities to inactivation on exposure to different oxidants. In this review, we discuss existing knowledge on the role that these enzymes play in the metabolism of cells, and their susceptibility to oxidation and inactivation with special emphasis on NADPH production. Perspectives on achieving a better understanding of the molecular basis of the oxidation these enzymes within cellular environments are given.
The ORAC (oxygen radical absorbance capacity) index does not reflect the capacity of antioxidants to trap peroxyl radicals
(2015) Dorta Pérez, Eva; Fuentes Lemus, Eduardo Felipe; Aspee, A.; Atala, E.; Speisky, Hernán; Bridi, Raquel; Lissi, E.; López Alarcón, Camilo Ignacio

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