China
Africa
Explore chapters and articles related to this topic
Reactivities of Amino Acids and Proteins with Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
It is thought that ubiquitous peroxidase may be responsible for such cross-links to occur. Indeed, detectable amounts of dityrosine can be formed in some proteins on oxidation with horseradish peroxidase,287,291 but apparently not in others (see Chapter 3, Section II.C.3.a).
Modifications of the Cell Surface Leading to Cell Elimination
Published in Alvaro Macieira-Coelho, Molecular Basis of Aging, 2017
Mixed function oxidases in metal-catalyzed reactions are the primary cause of oxidative protein damage.21 Hydroxyl radicals generated by this pathway oxidize arginine, proline, and lysine residues involved in metal coordination to semialdehydes, implying that proteins, like hemoglobin, are particularly vulnerable. Hydroxyl radicals, generated by ionization, damage proteins more randomly by generating methionine sulfoxide, tyrosine-tyrosine cross-links, and SS cross-links involving cysteines. Lipid peroxidation yields malondialdehyde and 4-hydroxynonenal,21 which modifies proteins by forming adducts with amino acid residues containing nucleophiles. Senescent erythrocytes indeed contain increased amounts of carbonyl-modified proteins,100 methionine sulfoxide,101,102 and have a sevenfold higher content of malondialdehyde phospholipid adducts.103 Dityrosine is produced in hemoglobin when erythrocytes are exposed to H2O2.104
The Influence of Dietary Protein Modification During Food Processing on Food Allergy
Published in Andreas L. Lopata, Food Allergy, 2017
As outlined above, protein oxidation represents the first step of nitration by formation of tyrosyl radicals. However, these radicals can also combine to 3,3-dityrosine, one predominant modification upon protein oxidation, resulting in crosslinking of proteins (Radi 2004) (Figure 9.1). The relevance of photo-oxidation in terms of structural properties has been shown for different milk proteins after light exposure. Dityrosine content apparently varied depending on secondary structure revealing highest amounts in the random coil proteins a-casein and ß-casein and lowest yields in the globular proteins BLG and lactoferrin. Other changes included partial loss of secondary structure, loss of tryptophan or altered tertiary structure (Dalsgaard et al. 2007).
Histological and biochemical investigation of the renoprotective effects of metformin in diabetic and prostate cancer model
Published in Toxicology Mechanisms and Methods, 2021
Pınar Koroglu-Aydın, Bertan Boran Bayrak, Ilknur Bugan, Omur Karabulut-Bulan, Refiye Yanardag
AOPPs are known as cross-linked protein products containing dityrosine. They are formed as a result of chlorination of aromatic groups such as tyrosine in proteins. Additionally, AOPPs are one of the reliable biomarkers used in the determination of oxidative stress (Capeillère-Blandin et al. 2004). In addition, it can also contribute to progression and/or suppression of tumor formation depending on its local concentration (Mishra et al. 2020). TNF-ɑ, proinflammatory cytokines, is produced by immune cells (mainly T-lymphocytes) such as leukocytes, macrophages, renal tubular epithelial cells, and vascular endothelial cells. TNF-ɑ has a very important role for inflammation, apoptosis and modulation of immune system, as well as tissue repair process (Mehaffey and Majid, 2017). Synthesis and secretion of TNF-ɑ is elevate by inflammation (Cheng et al. 2019). In the current study, AOPP, NO, and TNF-ɑ levels were statistically higher in cancer, diabetic and DC groups when compared to control rats. The reason for the increase in AOPP, NO and TNF-ɑ levels can be due to the deterioration of the balance between oxidant/antioxidant in favor of oxidants or increased inflammation. The present results are compatible with the findings Sharma et al. (2007) and Sefi et al. (2012). It was observed that metformin treatment to cancer, diabetic and DC groups reversed the aforementioned effects. Metformin may be responsible for the attenuation of protein oxidation, as well as expression of NO and TNF-ɑ synthesis in the kidney. The present results are in compliance with Nakatake et al. (2018) and Cheng et al. (2019).
Proteomic characterization of the human lens and Cataractogenesis
Published in Expert Review of Proteomics, 2021
Identification of lens protein crosslinking sites has been largely facilitated by manual interpretation of tandem MS [96,98,100]. Recent methodological and algorithmic advances in crosslinked peptide identification may facilitate a more extensive identification of cross-linked peptides [101]. To identify endogenous modification sites, bottom-up approaches have been used most frequently, and recent improvements to experimental preparation include strong cation exchange (SCX) enrichment of cross-linked peptides [102], O18 enrichment of cross-linked peptides facilitated by tryptic digest [103] and ultraviolet photodissociation assisted identification of dityrosine crosslinks after GC fractionation [104]. Mixed N14/N15 isotope labeling has also been used in vitro to differentiate intermolecular crosslinks from intramolecular [105]. Automated identification of cross-links has proven more difficult with multiple groups providing rapidly improving algorithms capable of identifying non-cleavable cross-links [106–110]. Altogether, there is a promising future for the identification of high-throughput, site-specific cross-linking sites in the lens with MS technologies. Future improvements in gas phase separations by ion mobility mass spectrometry and data searching improvements are promising directions for the future of cross-linking MS.
Metformin protects red blood cells against rotenone induced oxidative stress and cytotoxicity
Published in Archives of Physiology and Biochemistry, 2021
Shambhoo Sharan Tripathi, Abhishek Kumar Singh, Farhan Akhtar, Ankita Chaudhary, Syed Ibrahim Rizvi
Advanced oxidation protein products (AOPP) are a family of oxidised proteins. AOPPs belong to the category of dityrosine-containing protein products formed during oxidative stress and is a reliable marker for oxidant-mediated protein damage (Witko-Sarsat et al.1996, Witko-Sarsat et al.1998). Circulation of an elevated level of AOPP in plasma is an oxidative stress biomarker and can lead to immune dysregulation (Cristani et al.2016). In the present study, we observed that rotenone considerably elevated AOPP level in plasma. Interestingly, metformin supplementation significantly reverses the level of AOPPs in rotenone-exposed rats. It is known that metformin is useful for reduction of AOPPs level in diabetic patients (Chakraborty et al.2011).