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Effects of hypotaurine on carbonate radical anion and nitrogen dioxide radical generated by peroxidase activity of Cu,Zn-superoxide dismutase
No full textCysteine sulfinate (CSA) and hypotaurine are recognized as key intermediates in the metabolic pathway leading from cysteine to taurine. The oxidation of sulfinic group to the respective sulfonate is a crucial point for generation of taurine in mammalian tissues. The mechanism of sulfinic group oxidation could not be related to specific enzymatic activities. However, oxidizing agents, such as hydroxyl radical, photochemically generated singlet oxygen and peroxynitrite have been reported to accomplish such oxidation in good yield.
Carbonate radical anion (CO3 radical) is receiving increasing attention as important mediator of biological processes and is a potent one-electron oxidant that is able to oxidize a variety of biotargets. Nitrogen dioxide radical (NO2) is well known as a reactive species capable to initiate both oxidation and nitration reactions. The pathogenic role of radical NO2 has been related mostly to the increased level of nitrated proteins detected under many disease
Reaction of hypotaurine and cysteine sulfinic acid with CO3• ̄ and •NO2 generated by peroxidase activity of Cu, Zn-SOD: oxidative mechanism and protection
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Thiotaurine modulates human neutrophil activation
No full textNeutrophils are well recognized as one of the major players during acute infl ammation.They are typically the fi rst leukocytes to be recruited to an infl ammatory site and can eliminate pathogens by multiple means. Two different microbicidal mechanisms occur within the neutrophils: the oxidative and the non oxidative systems. The oxygen-dependent mechanism acts through generation of reactive oxygen species (ROS), and the oxygen-independent mechanism acts through production of antimicrobial peptides and proteolytic enzymes. During infl ammation, neutrophils are activated in response to several agonists generating superoxide anion and other ROS by NADPH oxidase-dependent mechanisms. This functional response, termed oxidative burst, contributes to host defense, but it can also result in collateral damage of host tissues. NADPH oxidase is a multicomponent enzyme system that catalyzes
NADPH-dependent reduction of oxygen to superoxide anion. NADPH oxidase is activated by a variety of agents including N -formyl-methionyl-leucyl-phenylalanine (fMLP) and the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA). These stimuli trigger biochemical cascades leading to the phosphorylation of several proteins of the NADPH oxidase system. In addition to the well-documented PKC pathway, one of these cascades involves activation of members of the mitogen-activated protein kinase (MAPK) family. Several studies have demonstrated that MAPK pathways such as extracellular signal- regulated kinases (ERK) 1/2 and p38 MAPK are activated in human neutrophils.
Taurine is the most abundant free amino acid in most animal tissues and plays an important role in several essential biological processes (Huxtable 1992 ). A large number of reports have demonstrated the key role of taurine and its derivatives in the innate immune response (Schuller-Levis and Park 2004 ). It is widely recognized that taurine and related compounds such as hypotaurine and taurine chloramine exert a regulatory role in acute infl ammation. The protection by taurine and its derivatives on infl ammatory injury may be due to modulation of NADPH oxidase activity. It is noteworthy that taurine chloramines decrease PMA-stimulated superoxide production in human neutrophils by inhibiting phosphorylation of subunits of NADPH oxidase, eventually blocking the assembly of NADPH oxidase complex. Recently, it has been shown that thiotaurine (2-aminoethane thiosulfonate), a biomolecule structurally related to hypotaurine and taurine, prevents spontaneous apoptosis of human neutrophils (Capuozzo et al. 2013 ) and counteracts the damaging effect of oxidants in diabetic rat (Budhram et al. 2013 ). Interestingly, thiotaurine contains a sulfane sulfur that can be released as hydrogen sulfi de (H 2 S). It has been shown that H 2 S plays relevant roles, modulating several pathophysiological processes, including infl ammation. Taken together, these observations raise the possibility that thiotaurine, analogously to taurine and its derivatives, could modulate neutrophil activation. Thiotaurine is a thiosulfonates (RSO 2 SH) which has been occasionally detectedamong the products of biochemical reactions involving sulfur compounds. Thiotaurine is a metabolic product of cysteine in vivo and is produced by a spontaneous transsulfuration reaction involving thiocysteine (RSSH) and hypotaurine (RSO2H). Moreover, a sulfurtransferase which catalyzes the transfer of sulfur from mercaptopyruvate to hypotaurine with production of thiotaurine has been also reported. In the present study, thiotaurine has been assessed for an activity on functional response of human neutrophils. The results reveal that thiotaurine modulates fMLP- and PMA-mediated activation of human neutrophils, by inhibiting total ROS generation and superoxide anion production. Compared with fMLP-activated neutrophils, PMA-activated neutrophils were more susceptible to thiotaurine inhibition, suggesting that thiotaurine may interfere with the PKC-dependent pathway of neutrophil activation
Oxidation of hypotaurine and cysteine sulfinic acid by peroxidase-generated reactive species
No full textHypotaurine (HTAU) and cysteine sulfinic acid (CSA) are the metabolic intermediates in the mammalian pathway leading from cysteine to taurine. Strong evidence has been presented that the formation of taurine (TAU) and cysteic acid (CA) is the result of the interaction of both sulfinates with various oxidizing agents that may be present in biological systems. The purpose of the present study is to investigate the oxidation of sulfinates, HTAU and CSA, by peroxidase-generated reactive species. Reactive nitrogen and oxygen species can be produced during the process of nitrite oxidation catalyzed by heme peroxidases, such as horseradish peroxidase (HRP) or myeloperoxidase, in the presence of hydrogen peroxide (H2O2). Nitrite is the major end product of nitric oxide (NO) metabolism. Oxidation of nitrite by such mechanisms could be important at sites of inflammatory processes. The formation of reactive nitrogen species (RNS) via peroxidase-catalyzed oxidation of nitrite could represent an a
Chemistry and Biochemistry of Sulfur Natural Compounds: Key Intermediates of Metabolism and Redox Biology
Full text linkSulfur contributes significantly to nature chemical diversity and thanks to its particular features allows fundamental biological reactions that no other element allows. Sulfur natural compounds are utilized by all living beings and depending on the function are distributed in the different kingdoms. It is no coincidence that marine organisms are one of the most important sources of sulfur natural products since most of the inorganic sulfur is metabolized in ocean environments where this element is abundant. Terrestrial organisms such as plants and microorganisms are also able to incorporate sulfur in organic molecules to produce primary metabolites (e.g., methionine, cysteine) and more complex unique chemical structures with diverse biological roles. Animals are not able to fix inorganic sulfur into biomolecules and are completely dependent on preformed organic sulfurous compounds to satisfy their sulfur needs. However, some higher species such as humans are able to build new sulfur-containing chemical entities starting especially from plants' organosulfur precursors. Sulfur metabolism in humans is very complicated and plays a central role in redox biochemistry. The chemical properties, the large number of oxidation states, and the versatile reactivity of the oxygen family chalcogens make sulfur ideal for redox biological reactions and electron transfer processes. This review will explore sulfur metabolism related to redox biochemistry and will describe the various classes of sulfur-containing compounds spread all over the natural kingdoms. We will describe the chemistry and the biochemistry of well-known metabolites and also of the unknown and poorly studied sulfur natural products which are still in search for a biological role
Reactivity of hypotaurine and cysteine sulfinic acid toward carbonate radical anion and nitrogen dioxide as explored by the peroxidase activity of Cu,Zn superoxide dismutase and by pulse radiolysis
No full textHypotaurine and cysteine sulfinic acid are known to be readily oxidized to the respective sulfonates, taurine and cysteic acid, by several oxidative agents that may be present in biological systems. In this work, the relevance of both the carbonate anion and nitrogen dioxide radicals in the oxidation of hypotaurine and cysteine sulfinic acid has been explored by the peroxidase activity of Cu,Zn superoxide dismutase (SOD) and by pulse radiolysis. The extent of sulfinate oxidation induced by the system SOD/Hydrogen Peroxide in the presence of bicarbonate (Carbonate anion radical generation), or nitrite (Nitrogen dioxide radical generation) has been evaluated. Hypotaurine is efficiently oxidized by the carbonate radical anion generated by the peroxidase activity of Cu,Zn SOD. Pulse radiolysis studies have shown that the carbonate radical anion reacts with hypotaurine more rapidly than nitrogen dioxide. Regarding cysteine sulfinic acid, it is less reactive with the carbonate radical anion than hypotaurine. It has also been observed that the one-electron transfer oxidation of both sulfinates by the radicals is accompanied by the generation of transient sulfonyl radicals. Considering that the carbonate radical anion could be formed in vivo at high level from bicarbonate, this radical can be included in the oxidants capable of performing the last metabolic step of taurine biosynthesis. Moreover, the protective effect exerted by hypotaurine and cysteine sulfinate on the carbonate radical anion-mediated tyrosine dimerization indicates that both sulfinates have scavenging activity towards the carbonate radical anion. However, the formation of transient reactive intermediates during sulfinate oxidation by carbonate anion and nitrogen dioxide radical may at the same time promote oxidative reactions.Hypotaurine and cysteine sulfinic acid are known to be readily oxidized to the respective sulfonates, taurine and cysteic acid, by several oxidative agents that may be present in biological systems. In this work, the relevance of both the carbonate anion and nitrogen dioxide radicals in the oxidation of hypotaurine and cysteine sulfinic acid has been explored by the peroxidase activity of Cu,Zn superoxide dismutase (SOD) and by pulse radiolysis. The extent of sulfinate oxidation induced by the system SOD/Hydrogen Peroxide in the presence of bicarbonate (Carbonate anion radical generation), or nitrite (Nitrogen dioxide radical generation) has been evaluated. Hypotaurine is efficiently oxidized by the carbonate radical anion generated by the peroxidase activity of Cu,Zn SOD. Pulse radiolysis studies have shown that the carbonate radical anion reacts with hypotaurine more rapidly than nitrogen dioxide. Regarding cysteine sulfinic acid, it is less reactive with the carbonate radical anio
The oxidation of the sulfinates, hypotaurine and cysteine sulfinate, by carbonate radical anion.
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Peroxidase-catalyzed oxidation of hypotaurine and cysteine sulfinate in the presence of nitrite
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