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The Noncollagenous Proteins of the Intervertebral Disc *
Published in Peter Ghosh, The Biology of the Intervertebral Disc, 2019
Elastin is a highly insoluble protein rich in hydrophobic amino acids and contains few polar functional groups. It is synthesized as a soluble precursor molecule, tropoelastin (mol wt 72,000), of similar amino acid composition to insoluble elastin, but contains additional lysine residues which are subsequently involved in cross-link formation. These convert the tyopoelastin to insoluble elastin. Cross-linking is achieved via aldehyde (allysine) formation derived from lysine residues by the enzyme lysyloxidase. The cross-links of elastin contain the unique amino acids desmosine and isodesmosine.78,79 Other cross-links have recently been described,80–83 some of which are identical to those present in collagen.84 However, all of the known cross links of elastin are derived from lysine, whereas hydroxylysine is also utilized in collagen cross-link formation. In mature elastin, dihydrodesmosine and dihydroisodesmosine are more prevalent than the desmosine and isodesmosine ring structures. Problems, however, are encountered in the unequivocal demonstration of cross-linking structures in mature elastin, since the harsh extractive conditions required for its solubilization partially destroy desmosine/isodesmosine and intermediate cross-link structures.85,86
Outdoor Air Pollution
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
Procollagen has to undergo an oxidation to become mature collagen. By oxidation, the lysine residue of procollagen becomes allysine and forms a bridge between two different trimers of procollagen. In case of OS, more residuals of lysine are oxidized to allysine and too many bridges are formed between procollagen trimers, and consequently the collagen becomes rigid and elastic. In this case, AOs may control the reaction and allow an efficient production of collagen, but once the rigidity occurs, they cannot enter sufficiently and rapid enough to counteract the oxidants.
Molecular Structure and Functions of Collagen
Published in Marcel E. Nimni, Collagen, 1988
Marcel E. Nimni, Robert D. Harkness
Cross-linking renders the collagen fibers stable and provides them with an adequate degree of tensile strength and visco-elasticity to perform their structural role. The degree of crosslinking, the number and density of the fibers in a particular tissue, as well as their orientation and diameter combine to provide this function. Cross-linking begins with the conversion to peptide-bound aldehydes of specific lysine and hydroxylysine residues in collagen. It involves the oxidative deamination of the e-carbon of lysine or hydroxylysine to yield the corresponding semialdehydes (allysine or hydroxyallysine) and is mediated by lysyloxidase.223–226 Since this enzyme remains tightly bound to collagen, purified by conventional precipitative methods, incubation of such collagen at 37°C, neutral pH, and physiological ionic strength will cause additional aldehydes to form on the molecule.226 This effect can be enhanced by tissue extracts that possess lysyl oxidase activity or by the purified enzyme. This strong affinity of lysyl oxidase for collagen has been used for purifying the enzyme by affinity adsorption.227 Enzymatic activity is inhibited by ß-aminopropionitrile by chelating agents such as EDTA and d-penicillamine at concentrations which are able to immobilize all the Cu2+ in the media and by isonicotinic acid hydrazide and other carbonyl reagents. Lysyl oxidase exhibits particular affinity for the lysines and hydroxylysines present in the nonhelical extensions of collagen, but can, at a slower pace, also alter residues located in the helical region of the molecule,228 It has been proposed that it binds initially to the carboxyl-terminal non-helical end of the fibrillar collagen, since it has been observed that the E-NH2 groups in this region are the first to be converted to aldehydes.229
Spatial composition and turnover of the main molecules in the adult glomerular basement membrane
Published in Tissue Barriers, 2023
David W. Smith, Azin Azadi, Chang-Joon Lee, Bruce S. Gardiner
While both types of collagen IV are found across the GBM, collagen IV α3α4α5 predominates in the lamina rara externa and lamina densa.28 The collagen IV protomers polymerize, joining at their NC1 domains (8.6 nm in diameter30) to form hexamers (about 11 to 12 nm in diameter30), while cross-linking occurs at the N-terminal 7s domains. The collagen IV network is stabilized by both sulfilimine and allysine-derived cross-links.34 Protomer polymerization provides structural integrity to the collagen IV network within the GBM. Recent research on Drosophila has shown that chloride ion concentration is important in enabling the formation of collagen IV hexamers, and Cummings et al. suggest that low chloride ion concentrations could help ‘reposition’ basement membrane components, by ‘disrupting’ the collagen IV assembly.35
Proteomic exploration of cystathionine β-synthase deficiency: implications for the clinic
Published in Expert Review of Proteomics, 2020
Collagen is a major structural protein component of connective tissues (e.g., skin, tendons, bone), which accounts for 25 to 35% of the total protein weight in mammals [93]. Normal function of collagenous fibers depends on inter-chain crosslinks, which stabilize triple helical structures [94]. Crosslinking is initiated by the oxidation of specific lysine and hydroxylysine residues to the aldehydes allysine and hydroxyallysine, respectively. The enzymatic oxidation reactions are catalyzed by lysine oxidase (LOX) [95,96]. Spontaneous chemical reactions between the allysine/hydroxyallysine residues and the ε-amino group of lysine residue afford a Schiff-base adduct, which converts to a stable pyridinoline crosslink [97]. Each triple-helical collagen unit contains one to two crosslinks. The fibril-forming type I, II, and III collagens have four cross-linking sites: one in each of the short non-helical ends, called telopeptides, and two in the triple-helical region, close to the N- and C-terminal ends of collagen molecules. The pyridinoline crosslinks, which occur in collagens of cartilage, bone, and skeletal tissues, provide the stability and tensile strength to collagen fibrils, which is important for the mechanical function of connective tissues [93,94].
Co-administration of resveratrol and beta-aminopropionitrile attenuates liver fibrosis development via targeting lysyl oxidase in CCl4-induced liver fibrosis in rats
Published in Immunopharmacology and Immunotoxicology, 2019
Roohollah Mohseni, Zahra Arab Sadeghabadi, Mohammad Taghi Goodarzi, Jamshid Karimi
The RES administration relived oxidative stress via increasing TAC and -SH and decreasing TOS and MDA level in the liver homogenate during the CCl4 hepatotoxicity. Zhang et al. showed the levels of MDA and TAC were decreased in response to the RES administration in pulmonary fibrosis model [28]. Also, the effect of RES was similar to quercetin. Quercetin inhibited elevation of MDA and increased –SH and activity of superoxide dismutase, catalase, and glutathione peroxidase in the liver homogenate of CCl4-treated rats [29]. LOX enzyme catalyzes the conversion of lysine residues of collagen and elastin to allysine. During this reaction, H2O2 is released. As a result, inhibition of LOX decreases H2O2 content. Martı´nez-Revelles showed BAPN reduces oxidative stress in hypertensive models via inhibition of LOX enzyme [30]. Contractile to our expectation, in the present study BAPN did not modify oxidative stress parameters. However, co-administration of RES and BAPN improved hepatic oxidative stress status. These results verify serum biochemical data that showed RES improves the hepatoprotective effect of BAPN.