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Carbonylation

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Last Updated: 02 July 2021

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P rotein carbonylation is a type of protein oxidation that can be promoted by reactive oxygen species. It usually refers to a process that forms reactive ketones or aldehydes that can be reacted by 2 4-dinitrophenylhydrazine to form hydrazones. Direct oxidation of side chains of lysine, arginine, proline, and threonine residues, among other amino acids, in primary protein carbonylation Reaction produces DNPH detectable protein products. DNPH derivatizable protein products can also be form in secondary protein carbonylation Reaction via addition of aldehydes such as those generated from lipid peroxidation processes. Oxidative decomposition of polyunsaturated fatty acids initiates chain reactions that lead to formation of a variety of carbonyl species, most reactive and cytotoxic being,-unsaturated aldehydes, di-aldehydes, and keto-aldehydes. Although the biology of oxidative protein modifications is complex and remains define, protein carbonylation and chemistry of reactions that give rise to carbonyl groups have been well characterize. Development of antibody against DNPH-derivatized proteins revolutionalized studies of carbonylated proteins by allowing for use of immunological techniques. More recently, these methods have contributed to rapid progress in proteomic analyses of carbonylated proteins using two-dimensional gel electrophoresis, followed by immunoblotting and mass spectrometry. This redox proteomics approach allows for identification of carbonylated proteins in various diseases in humans, animal models, and cell models, and has provided important information to biologists by describing effects of modifications by carbonyl species on protein function, as well as the consequences of such modifications at the cellular level. Butterfield and CO-workers developed this proteomics approach to identify specifically oxidized proteins in Alzheimer's disease by detecting carbonylated proteins. In this issue, Sultana et al. Use redox proteomics approach to identify specifically carbonylated proteins in inferior parietal lobule from human subjects with mild cognitive impairment and early stage Alzheimer's disease, providing insights into the mechanism of progression of this disease. Hussain, Barreiro and CO-workers have championed understanding of carbonylated proteins in skeletal muscle dysfunctions during various disease processes such as chronic obstructive pulmonary disease and sepsis. In this issue, Barreiro and Hussain review their studies on carbonylated proteins in skeletal muscle dysfunction. Further, Barreiro and CO-workers report their data on carbonylated proteins in skeletal and cardiac muscle of cachectic rats. Burcham and CO-workers have previously shown that cell exposure to acrolein results in reaction with cysteine groups, forming protein carbonyls. In this issue, Burcham et al. Demonstrate that intermediate filament proteins are targets of acrolein-induced protein carbonylation in A549 lung epithelial cells, providing evidence for involvement of carbonylation of these proteins during smoke-induced lung injury. In addition to identification of proteins that are carbonylated in various disease models, advancement in mass spectrometry technology has allowed for sophisticated mechanistic studies of carbonylated proteins in oxidative stress conditions. In this issue, Dalle-Donne and CO-workers report identification of amino acids within human serum albumin molecules that are carbonylated in response to cigarette smoke extract exposure.

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* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions

Protein carbonylation

Rapid carbonylation of mistranslate or otherwise aberrant proteins points to an important physiological role of carbonylation in protein quality control. Since Carbonylated proteins ARE more susceptible to proteolytic degradation than their nonoxidized counterparts, rapid carbonylation of erroneous protein may ensure that such polypeptide is direct to proteolysis apparatus. Thus, carbonylation may act as a signal ensuring that damaged proteins enter degradation pathway rather than chaperone / repair pathway since carbonylation is an irreversible / unrepairable modification. This could effectively reduce incorporation of mistranslated proteins into mature machines involved in information transfer. In line with this notion, Carbonylated proteins generated as result of increased mistranslation were found to be less stable than average bulk protein and the degree of Carbonylated proteins in mature ribosomes is small in healthy cells of E. Coli. Another potentially important role of carbonylation is its involvement in autophagylike mechanisms. In this context, carbonylation may act as a mechanism providing amino acids for de novo Protein synthesis by targeting proteins that ARE NO longer require, or have become damaged / aberrant, for degradation. It is not clear whether carbonylation and ubiquitinylation operate independently or in concert in tagging protein for degradation in eukaryotic cells. However, fact that carbonylation of Protein isolate from E. Coli is recognized by mammalian proteasome in vitro suggests that carbonylation may bypass the need for ubiquitinylation, at least in this specific case. Abovementioned carbonylation of aberrant proteins is rather unspecific and ONE may ask how cell can achieve specificity using carbonylation as marker for Protein degradation. In other words, how can, for example, specific degradation of glutamine synthetase be achieved during nitrogen starvation by carbonylation reaction? As mention, introduction of carbonyl groups in this enzyme marks it for subsequent degradation upon nitrogen starvation. ONE possibility for such specific carbonylation of enzyme during ammonium starvation is that idle enzyme, like aberrant proteins, is more susceptible to oxidative carbonylation. Enzymes ARE frequently found to be protected by their substrates from proteolysis. Thus, certain enzymes become more susceptible to degradation during conditions where their substrates ARE present at diminishing levels. This is conceivably due to subtle conformational differences in working and unoccupied forms of enzyme. If idle form of glutamine synthetase is more susceptible to oxidative carbonylation, this may impart apparent specificity and regulation of carbonylationdependent tagging for Protein degradation during ammonium starvation. A summary of possible mechanisms rendering protein more susceptible to carbonylation, and therefore degradation, is illustrated in Figure 2. It is conceivable that any condition, such as elevated temperatures, exposure to denaturing agents, and limitations or defects in molecular chaperone systems, could cause elevated concentration of aberrant proteins and therefore increased carbonylation. However, so far, only means of generating aberrant proteins that have been shown experimentally to elevate carbonylation ARE those affecting the proofreading capacity of the ribosome.

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6.1.1 Introduction to Carbonylation Chemistry

Carbonylation generally refers to a group of closely connected reactions in which a molecule of CO is incorporated into substrate. This either takes place by insertion of CO into existing bond, or by addition and insertion of CO into unsaturated compounds such as alkynes or alkenes in the presence of different nucleophiles. 1 latter reaction is more closely related to hydroformylation reaction, 2 in which formyl group get attached to olefinic double bond. Even though hydroformylation comes under a class of reactions which are termed carbonylation, it is, however, treated separately due to its immense industrial significance. Hence, carbonylation reactions are of great interest to synthetic chemists as they allow construction of new bonds, along with simultaneous introduction of carbonyl group. In the late 1930s and early 1940s, W. Reppe at BASF worked immensely in this area and also coin-term carbonylation. Over the last five decades, carbonylation reactions have gained tremendous importance in different branches of chemistry. In the present era, hydroformylation and alcohol carbonylation represent core industrial technology and are the most significant branches of carbonylation Chemistry.

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10.4.3.1.(iii) CO insertion

Insertion of CO into transition-metal-alkyl bond is generally a key step in catalytic Carbonylation reactions, including important commodity chemical transformations such as hydroformylation and methanol Carbonylation to give acetic acid, as well as numerous reactions widely applied in synthesis of fine chemicals. In the early 1960s, it was discovered that rates of CO insertion could be markedly increased by polar solvents such as THF or DMF; effect was originally attributed to variations in dielectric constant of the environment. In 1981, Wax and Bergman demonstrated that the ability of THF and substitute derivatives to promote insertion correlate strongly with the ability of the promoter to act as electron-pair donor, rather than with its dielectric constant. Base on this finding, in conjunction with results of kinetic experiments, it was concluded that the promotion effect operates via addition of solvent to alkyl metal carbonyl complex to induce CO insertion, followed by associative attack of trap on S-coordinated acyl complex to give product, indicated as L n M in Fig. 1. It was subsequently shown by Webb, Giandomenico, and Halpern that triphenylphosphine oxide was a far more effective catalyst than typical polar solvent molecules. Authors then conducted kinetic studies which demonstrate that the catalytic mechanism involves dissociation of Ph 3 PO from complex before addition of T. It was therefore concluded that solvent, or more accurately in this case, nucleophile, catalyze formation of coordinatively unsaturated L n M. In the original report by Webb, Giandomenico, and Halpern, trap use was H-Mn 4; upon reaction of hydride with acyl complex, and addition of CO, this lead to formation of 5 Mn-Mn 4 and P-methoxybenzaldehyde. The role of the nucleophile as catalyst for insertion reaction was quite difficult to explain; indeed, Webb, Giandomenico, and Halpern offer no explanation. In particular, it seems implausible that coordination of S to vacant coordination site of LnM would facilitate migration of alkyl group to that formerly empty site. It has been proposed that the role of nucleophile is to attack the carbon center of ancillary CO ligand, in analogy with known reactions of amine oxides and other nucleophiles. It is still not at all obvious, however, how such a nucleophilic attack would facilitate CO insertion / deinsertion. In this contribution, we present Computational evidence that the role of nucleophile is not actually as proposed in these or any other earlier reports. Unexpectedly, it is found that nucleophile do not promote CO insertion reaction step. Instead, our calculations reveal that its role is to catalyze isomerization of initial product of CO insertion, to give product that is more easily trap. Moreover, calculations capture remarkably well experimentally determine ordering of reactivity of wide range for nucleophile catalysts.

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9.9 Carbonylation

Legumes establish nitrogen-fixing symbioses with soil bacteria, collectively know as rhizobia. Perception of rhizobial nodulation factors by host plant induces a cascade of responses that lead to bacterial and root cell differentiation and nodule development. Nodules provide optimal conditions for expression of bacterial nitrogenase, whose activity contributes fix nitrogen to ecosystems and croplands. These unique symbiotic organs show high metabolic rate to meet the considerable energy demand of nitrogen fixation. As a result, they produce large amounts of reactive oxygen species that need to be kept under control by antioxidant enzymes and metabolites. ROS may oxidize proteins reversibly or induce their irreversible modification. Metal-catalyze oxidation occurs when free Fe 2 + or Cu + reacts with hydrogen peroxide and generates highly reactive hydroxyl radicals through Fenton reaction. These radicals can oxidize almost any amino acid side chain, although some of them are particularly susceptible to carbonylation. Carbonyl groups also may be generated indirectly. In cell membranes, lipid peroxidation takes place when highly reactive ROS, mostly hydroxyl radicals and singlet oxygen, abstract hydrogen atom from polyunsaturated fatty acids to form lipid hydroperoxides. These molecules are unstable and decompose to generate reactive aldehydes and Ketones that form covalent Michael adduct with Arg, Cys, His, and Lys residues. Moreover, Arg and Lys residues can react with reducing sugars via formation of imine intermediate, generating Amadori and Heyns compounds. These glycation products are readily oxidize, yielding relatively stable advanced glycation end products. Alternatively, AGEs can be form by reaction to Glyoxal and methylglyoxal are generated by monosaccharide autooxidation or via Namiki pathway, whereas 3-deoxyglucasone is product of nonoxidative enolization and dehydration. Protein carbonylation occurs in animal and plant tissues and contributes to cellular damage caused by stress conditions and age-associate diseases. Recent studies, however, suggest that irreversible protein oxidation might be a major event regulating protein biological function and fate. Carbonylation of nodule proteins is likely to be important because nodules contain high amounts of Fe proteins, such as nitrogenase, cytochromes, and leghemoglobin, which are prone to oxidation. Protein glycation is well characterized in mammals under several physiological conditions. In humans, formation of AGEs accompanies atherosclerosis and diabetes. These modifications target mostly long-living proteins, like human lens proteins and collagen, but also plasma proteins. Interestingly, analysis of protein hydrolysates revealed high levels of glycation in plants. This result was confirmed at proteome level, especially under abiotic stress conditions. Nevertheless, investigation of protein carbonylation and advanced glycation in plants is still in its infancy. Identification of oxidized amino acid residues in proteins may provide essential information about oxidative mechanisms and metabolic pathways involved in loss of cellular viability that occur during aging and under stress conditions. Thus, our aim was to gain insight into these processes in vivo using nodulated plants of bean, major grain legume for direct human consumption.

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4.1.2.2 Substitutive Carbonylation

Direct carbonylation of organic halide is a rather rare synthetic process and systems in which halide ion is replaced by nucleophile are much more frequently encounter. This is a particularly versatile type of reaction providing a wide range of acyl anion equivalents, which allows synthesis of many carboxylic acid derivatives from organic halides. As example, elementary steps involved in palladium-catalyzed carbonylation of bromoarene are shown in Scheme 5, where oxidative addition is followed by CO insertion and reductive cleavage by whichever nucleophile is present in the system. Substitutive carbonylation of aliphatic halides is also possible, but generally requires more vigorous conditions and use of platinum-phosphine complexes, such as.

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2.2.1.3.(i) Monodentate nitrogen-donor ligands

New examples of cis-RhLCl 2 were obtained from bridge-splitting reactions of 2. These include L =, 89 90 91 R 1 3 P NR 2 92 phenazine, 93 phenazine oxide, 93 N-methylimidazole, 94 N-benzylimidazole, 94 3 5-dimethylpyrazole, 95 benzotriazole, 96 PhNO, 97 1-tetralone oximes, 98 ethanolamine 99 9-methylguanine, 100 hypoxanthene, 100 cytosine, 100 1-methylcytocine, 100 guanosine, 100 1-methylguanosine, 100 inosine, 100 adenosine, 100 cytidine, 100 7-deazaadenosine, 100 8-azaguanine, 101 9-methylallopurinol, 101 allopurinol, 101 8-aza-9methyladenine, 102 and 8-aza-9benzyladenine. 102 Liquid crystals were obtained with mesogenic organic ligand. 103 Carbonylation of cod analogues was the second route, and was used to prepare mesogenic Complexes for L =. Second L = was added to produce monocarbonyls, trans-rhcll 2 P 3 was also used to displace CO to produce RhCl 3l. 104 complexes of type L = 1H-pyrrolopyridine 105 and + L = 1H-pyrrolopyridine, 105 indazole, 106 1 8-naphthyridine 107 were also made by Carbonylation of diene analogues. Neutral Complexes 61 R = H, F were obtained by disruption of dimers 2 with L = 60 N = 2 8 14. Alternatively, these complexes were prepared by Carbonylation of cod analogues. Heating these Complexes with Me 3 NO gives green tetranuclear 62 R = H, F; L = 60 N = 2 8 14, py.

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Carbonylationfriend or foe?

It has been argued that oxidative modification of protein makes it more susceptible to proteolysis largely due to unfolding of target protein domains. Unfolding results in increased exposure of hydrophobic residues that are normally hidden in the interior of soluble proteins and such hydrophobic patches are known to favor recognition and degradation by proteasome and Lon protease. Partly aberrant unfolded protein exposes aminoacid residues normally hidden in protein structure, and introduction of carbonyl groups on those amino acids may simply result in further loss of protein's integrity. In this scenario, carbonylation is just one of many possible oxidative modifications that may render protein more prone to degradation. Since carbonylation is unrepairable, this modification may, however, be of special importance in directing affected protein to a path toward degradation. Described functions of carbonylation point to a beneficial role in protein quality control and protein metabolism. However, it turns out that carbonylation may be mixed blessing. For example, while mildly carbonylated aconitase is mark for proteolysis, heavily oxidized form of enzyme tends to form highmolecularweight aggregates that escape degradation by mitochondrial Lon protease. In addition, aggregates of severely oxidized proteins are poor substrates for proteasome and such aggregates can inhibit proteasome activity. It has been suggested that decline in proteosomal activity during aging may, in fact, be closely connected to gradual accumulation of proteolysisresistant aggregates of oxidized proteins that bind and inhibit proteosomal function. Further, it is argued that this mechanism of inhibition of proteasome is more dramatic in postmitotic cells, for example, neurons, than dividing cells since the latter can effectively dilute damaged proteins and aggregate by growth and proliferation.

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Conclusion

Changes in the level of carbonylated proteins during the life of tree. Progression of plant Ageing. The highest level of proteins mark with CO groups is achieved at last part of life-span. B Seasonal, environmental-dependent changes. Leaf senescence is not linked to ageing of the whole plant organism and is accompanied by an increase in carbonylated protein level. Lowest content of oxidized proteins is achieved before production of offspring. Most common pathways of protein carbonylation include direct ROS attack on amino acid residues, metal-catalyse oxidation attack on Lys, Arg, Pro and Thr residues in presence of ROS and reduced metal ions, adduction of advanced glycation end products form in presence of ROS, reduce metal ions and reducing sugars, eg glucose, and incorporation of products of lipid peroxidation, eg 4-hydroxynonenal. R represents amino acid residue of targeted protein for carbonylation

* Please keep in mind that all text is machine-generated, we do not bear any responsibility, and you should always get advice from professionals before taking any actions.

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Sources

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