Oxidation Of Tyrosine Residues Research Articles

Age-Related Diseases and Foods Generating Chlorinative Stress.

Aging is a slow and inexorable process affecting all life beings and is characterised by age-related worsening in adaptation to external changes. Several factors contribute to such a process, and oxidative stress due to external damages is one key player. Of particular interest is the oxidative stress generated from halogen compounds such as chloride. Hypochlorus acid is produced starting from MPO's interaction with hydrogen peroxide. We focused on the oxidation of tyrosine residues by HOCl, which leads as a result to the formation of 3-chlorotyrosine (3-ClTyr). This molecule, due to its stability, is considered a marker for MPO activity. We collected data from literature research articles evaluating chlorinative stress and the effects of 3-ClTyr on chronic diseases linked to aging. As diseases are not the only source of 3-ClTyr in people, we also focused on other origins of chlorinative stress, such as food intake. Oxidation and halogenation are caused by infectious diseases and by pathologies characterised by inflammation. Moreover, diet could negatively or positively influence chlorinative stress. Comparing 3-ClTyr levels in the oldest and youngest old with age-related diseases and comparing data between different geographic areas with different pesticide rules could be the next challenge.

The Effect of the Acidic Gas Pollutant on Wool Keratin Fiber Structure

ABSTRACT Increase in air pollution caused by acidic gases, such as nitrogen dioxide, call for the need to study potential effects on the structure of textile materials. Wool is a natural protein fiber which is easily damaged due to rich reaction positions and cross-linked bonds in the fiber. This study reports, for the first time, effect of nitrogen dioxide, as a model acid gas pollutant, on the structure of wool. On the macro level, wool fabric undergoes strength loss after incubation in nitrogen dioxide for 6 h. Furthermore, although there was no obvious difference on the surface morphology as shown by SEM analysis, FTIR and Raman tests showed that the probable damage mechanism is by hydrolysis of amino bond, and oxidation of tyrosine residues and disulfide bonds, which was ascertained using XPS and amino acid analysis. In addition, crystallinity degree and α-helix structure content decreased after nitrogen dioxide treatment as shown by XRD and NMR results. These findings show that nitrogen dioxide has significant effect on the structure of wool. The study offers a novel approach for investigation of the interaction between gas pollutants and protein fiber, and provide information for protection of textiles against similar pollutants.

The effects of nitric oxide or oxygen on the stable products formed from the tyrosine phenoxyl radical

Tyrosine is a critical component of many proteins and can be the subject of oxidative posttranslational modifications. Furthermore, the oxidation of tyrosine residues to phenoxyl radicals, sometimes quite stable, is essential for some enzymatic functions. The lifetime and fate of tyrosine phenoxyl radicals in biological systems are largely driven by the availability and proximity of oxidants and reductants. Tyrosine phenoxyl radicals have extremely low reactivity with molecular oxygen whereas reactions with nitric oxide are diffusion controlled. This is in contrast to equivalent reactions with tryptophanyl and cysteinyl radicals where reactions with oxygen are much faster. Despite, the quite disparate apparent reactivity of tyrosine phenoxyl radicals with oxygen and nitric oxide being known, the products of the reactions are not well established. Changes in the levels from expected basal concentrations of stable products resulting from tyrosine phenoxyl radicals, for example naturally occurring 3,3′-dityrosine, 3-nitrotyrosine, and 3-hydroxytyrosine, can be indicative of oxidative and/or nitrosative stress. Using the radiolytic generation of specific oxidizing radicals to form tyrosine phenoxyl radicals in an aqueous solution at a known rate, we have compared the products in the absence and presence of nitric oxide or oxygen. Possible reactions of the phenoxyl radicals with oxygen remain unclear although we show evidence for a small decrease in the yield of dityrosine and loss of tyrosine in the presence of 20% oxygen. Low concentrations of nitric oxide in anoxic conditions react with tyrosine phenoxyl radicals, by what is most probably through the formation of an unstable intermediate, regenerating tyrosine and forming nitrite.

Silk Hydrogels Crosslinked by the Fenton Reaction.

Here, the Fenton reaction is used to prepare silk hydrogels through oxidation of tyrosine residues in silk fibroin, leading to dityrosine crosslinking. At pH 5.7, gelation occurs rapidly within 30 s, and the resultant opaque gels show soft properties with a storage modulus of ≈100 Pa. The addition of ascorbic acid to the Fenton reaction increases the dityrosine bonds in the hydrogels but has little effect on the rheological or mechanical properties. The results indicate that Fe(III) ions significantly interacted with silk fibroin during the Fenton reaction, most likely binding to sites such as tyrosine, glutamate, and aspartate residues, triggering the formation of β-sheet structures that may impede dityrosine bond formation due to steric hindrance. The use of an iron chelator or the operation of the Fenton reaction at pH 9.2 enables control over the interaction of Fe(III) ions with silk fibroin, achieving a hydrogel with improved optical properties and enhanced dityrosine bond formation. Hydrogels prepared by the Fenton reaction are cytocompatible as L929 mouse fibroblasts remain viable and are proliferative when seeded on the hydrogels. The results offer a useful approach to generate chemically crosslinked silk fibroin hydrogels without the use of enzyme-catalyzed reactions for biomedical applications.

Immobilization of cell adhesive peptide on polymeric and metallic surfaces using dopaquinone produced by the direct oxidation of tyrosine residue

Immobilization of cell adhesive peptide on polymeric and metallic surfaces using dopaquinone produced by the direct oxidation of tyrosine residue

Oxidation and nitration of α-synuclein and their implications in neurodegenerative diseases

Synucleinopathies include Parkinson’s disease, dementia with Lewy bodies, Lewy body variant of Alzheimer’s disease and multiple system atrophy, among the most relevant diseases. All of these diseases are characterized by the presence of amyloid inclusions in neurons, which are rich in the aggregate α-synuclein protein. What is the biological mechanism concerned in the gain-of-function that implicates the participation of α-synuclein in these diseases? Post-translational modifications of α-synuclein induced by nitroxidative stress are a relevant hypothesis that may explain many of the experimental data. We will review the biophysical and biochemical properties of α-synuclein, methionine residues oxidation, nitration and oxidation of tyrosine residues in α-synuclein, and modifications of α-synuclein mediated by proteins and lipids under nitroxidative stress conditions. The biological consequences of these modifications are analyzed in terms of the properties of α-synuclein oligomerization and fibrillation, degradation of α-synuclein and the implications in the immunological response.

Enzymatic cross-linking of gelatine with laccase and tyrosinase

Conventional cross-linking of proteins involves the use of toxic chemicals. Here, cross-linking of gelatine and gelatine hydrolysates with tyrosinases from Botryosphaeria obtusa (BoT1 and BoT2), Agaricus bisporus (AbT) and from Verrucomicrobium spinosum (VsT) and with laccases from Trametes hirsuta (ThL) and T. versicolor (TvL) was demonstrated. Enzymatic oxidation of tyrosine residues was indicated by UV/VIS and fluorescence spectroscopy and further confirmed by oxygen consumption measurements. Using a model substrate (Tyr-Ala) dimerization was demonstrated by using RP-HPLC and LC-MS. Enzymatic cross-linking significantly increased the molecular weight of the soluble material up to the point of precipitation as demonstrated by both SDS-PAGE and size exclusion chromatography. The effect of cross-linking was further enhanced in the presence of phenolic molecules such as catechin.

Light‐induced protein and lipid oxidation in low‐fat cheeses: Effect on degree of enzymatic hydrolysis

The effect of proteolysis on oxidation in low‐fat cheese was investigated. The accumulation of dityrosine during storage increased significantly in the cheese with a high degree of proteolysis, while hexanal and heptanal were lower in the cheese with high proteolytic activity, indicating that the peptides/free amino acids acted as antioxidants on the propagating step in lipid oxidation. Dimethyl disulphide concentration was also lower in the cheese with a higher level of peptides. Therefore, oxidation of tyrosine residues seemed to function as antioxidants both regarding secondary lipid oxidation products and protein‐derived oxidation products through formation of dityrosine, being a termination reaction.

Comparing native and irradiated E. coli lactose repressor-operator complex by molecular dynamics simulation

The function of the E. coli lactose operon requires the binding of the tetrameric repressor protein to the operator DNA. We have previously shown that gamma-irradiation destabilises the repressor-operator complex because the repressor gradually loses its DNA-binding ability (Radiat Res 170:604-612, 2008). It was suggested that the observed oxidation of tyrosine residues and the concomitant structural changes of irradiated headpieces (DNA-binding domains of repressor monomers) could be responsible for the inactivation. To unravel the mechanisms that lead to repressor-operator complex destabilisation when tyrosine oxidation occurs, we have compared by molecular dynamic simulations two complexes: (1) the native complex formed by two headpieces and the operator DNA, and (2) the damaged complex, in which all tyrosines are replaced by their oxidation product 3,4-dihydroxyphenylalanine (DOPA). On a 20 ns time scale, MD results show effects consistent with complex destabilisation: increased flexibility, increased DNA bending, modification of the hydrogen bond network, and decrease of the positive electrostatic potential at the protein surface and of the global energy of DNA-protein interactions.

A novel and efficient synthesis of DOPA and DOPA peptides by oxidation of tyrosine residues with IBX

An efficient route to 3,4-dihydroxylphenylalanine (DOPA) and DOPA peptides was described by oxidation of l-tyrosine and l-tyrosine derivatives with 2-iodoxybenzoic acid (IBX). DOPA was obtained after an situ reduction of the corresponding ortho-quinone with sodium dithionite. Oxidation reactions proceeded in good yields and high chemo- and regio-selectivity. The chirality of the DOPA residue was retained under the reaction conditions. The efficiency and the selectivity of the reaction were successfully tested using recyclable polymer-supported IBX.

Evidence that DOPA-Derivatives are Generated After L-DOPA Incorporation into Proteins by Mammalian Cells

The adhesive and cohesive properties of the amino acid L-3,4-dihydroxyphenylalanine (DOPA) have been widely explored as a potential material for adhesion, based, among other things, on the biological system of blue mussel extracellular byssal threads and foot proteins. Proteins containing DOPA are generated within mammalian cells by oxidation of tyrosine residues during periods of oxidative stress. By generating proteins containing DOPA, in vitro, through the (mis)incorporation of DOPA during protein synthesis, we are able examine the role and fate of DOPA-containing proteins in mammalian cells. We demonstrate a decrease in catabolism of long half-life cell proteins and an increase in cellular autofluorescence when DOPA is present in cell proteins. We provide evidence for the formation of DOPA derivatives which can be detected in proteins after 14C-DOPA incorporation by HPLC analysis. Additionally, we demonstrate that the cells upregulate the expression of genes required to handle damaged proteins and protein aggregates under these conditions. Substantial evidence for DOPA derivatives and cross-linking has previously been shown in extracellular blue mussel byssal threads; here we provide evidence for cell-associated DOPA derivatives in mammalian cells.

Tyrosinase-Catalysed Coating of Wool Fibres With Different Protein-Based Biomaterials

The potential of tyrosinases to activate tyrosine residues of wool protein fibres for cross-linking with different materials like collagen, elastin and gelatine was assessed. Natural fibres like wool offer an excellent environment for the growth of micro-organisms when the conditions like moisture, oxygen and temperature are appropriate. Coating with collagen, a very useful biomaterial with bactericidal and fungicidal properties, could be used to improve the properties of wool-based materials, especially when applied in hygienically sensitive applications like in hospitals. Tyrosinases were shown to catalyse the oxidation of tyrosine residues in wool and wool hydrolysates as model substrates, as determined by UV-Vis spectroscopy. Structural differences of the surface were evident from the increase of the intensity in the NH bending and stretching regions in the spectra of NIR FT Raman analysis of the enzyme treated and grafted wool fibres. The durability of the coating was also shown by using FITC-labelled collagen that was bound to the wool fibres, even after severe washing. Additionally, antimicrobial properties were successfully imparted due to the collagen grafted on the wool fibres. The functional and mechanical properties of the treated wool fibres showed no significant changes.

Mass Spectrometric Elucidation of Phenolic Oxidation Processes with Cu2+-Adduct

Formation of e complex with 2-hydroxy-6-[8′(Z),11′(Z),14′-pentadecatrienyl]benzoic acid (anacardic acid) and copper ion in the respective ratios of 2 : 1 and 1 : 1 at room temperature was observed by electrospray ionization mass spectrometry. The oxidation of 3-(3,4-dihydroxyphenyl)alanine (DOPA) in the presence of anacardic acid showed competitive inhibition with temporary reduction from dopaquinone to DOPA. In the oxidation of neurotensin, the oxidized products, dopaquinone-derivatives, were observed. Mass spectrometry revealed that the enzymatic oxidation of tyrosine residue is inhibited by anacardic acid.

Simultaneous determination of 3-nitro tyrosine, o-, m-, and p-tyrosine in urine samples by liquid chromatography–ultraviolet absorbance detection with pre-column cloud point extraction

Stable 3-nitro tyrosine (3-NO 2-Tyr), o-, m-, and p-tyrosine isomers induced by oxidation of tyrosine residues in protein were considered important biomarkers for the existence of toxic oxidizing agents peroxynitrite (ONOO −) and OH , which could lead to such diseases as acute lung injury, neurodegenerative disorders, atherosclerosis, cancers and many other diseases. Therefore, development of an accurate, simple and sensitive method to simultaneously detect o-, m-, and p-tyrosine and 3-NO 2-Tyr is necessary. Fluorescence detection is highly sensitive to o-, m-, and p-tyrosine, but it cannot be used to detect 3-NO 2-Tyr, due to the strong fluorescence-quenching characteristic of the NO 2 group. In this study, we developed a highly sensitive reversed HPLC–UV method, combined with pre-column cloud point extraction (CPE), to simultaneously determine o-, m-, and p-tyrosine and 3-NO 2-Tyr. The procedure included derivatization of a sample with 6-aminoquinolyl- N-hydroxy-succinimidyl carbomate (AccQ) at 0.20 mol/l borate buffer (pH 8.80) for 30 min at 70 °C, and pre-concentration with surfactant cloud point extraction. The surfactant-rich phase was then diluted with deionized water and injected directly into the to HPLC column for analysis. A C 18 column (3.9 mm i.d. × 300 mm) was used for gradient elution separation at 25 °C and the detection wavelength was at 254 nm. Nineteen general amino acids showed no interference. The detection limits of p-, o-, m-Tyr and 3-NO 2-Tyr were between 5 and 15 nmol/l. The linear range was from 0.05 to ∼100 μmol/l.

Oxidation of tyrosine residues in proteins by tyrosinase. Formation of protein-bonded 3,4-dihydroxyphenylalanine and 5-S-cysteinyl-3,4-dihydroxyphenylalanine.

A simple and rapid method was developed for the determination of 3,4-dihydroxyphenylalanine (dopa) and 5-S-cysteinyl-3,4-dihydroxyphenylalanine (5-S-cysteinyldopa) in proteins with the use of high-pressure liquid chromatography. With this method, it is demonstrated that mushroom tyrosinase can catalyse hydroxylation of tyrosine residues in proteins to dopa and subsequent oxidation to dopaquinone residues. The dopaquinone residues in proteins combine with cysteine residues to form 5-S-cysteinyldopa in bovine serum albumin and yeast alcohol dehydrogenase, whereas dopa is the major product in bovine insulin, which lacks cysteine residues.

Formation of dityrosine cross-links in proteins by oxidation of tyrosine residues

1. 1.|Enzymic oxidation of proteins with peroxidase and hydrogenperoxide at a basic pH value leads to an oxidative phenolic coupling of adjacent tyrosine residues forming cross-linked proteins. 2. 2.|Dityrosine (3,3′-bityrosine) was identified as the cross-link in oxidised proteins by thin-layer chromatography, amino acid analysis and fluorescence measurements. 3. 3.|Gel filtration experiments with oxidised insulin showed that the cross-linkage is predominantly intermolecular. 4. 4.|In tetranitromethane treated proteins, dityrosine could be identified after hydrolysis.