Search results for "Glycosyl"
showing 10 items of 317 documents
Collagen overglycosylation: a biochemical feature that may contribute to bone quality.
2005
Skeletal ability to resist mechanical stress is determined by bone amount and quality, which relies on macro- and micro-architecture, turnover, bone matrix, and mineralisation; the role of collagen has not been clearly elucidated. Numerous post-translational steps are involved in collagen type I biosynthesis, including residue hydroxylation and glycosylation catalysed by enzymes that work until the protein folds forming the triple helix; therefore, folding rate regulates these processes. Overglycosylated hydroxylysines are poor substrates for epsilon-amino group deamination which initiates cross-link formation. Three clinical conditions associated with fractures may relate collagen overglyc…
Sulfated and Non-Sulfated Glycopeptide Recognition Domains of P-Selectin Glycoprotein Ligand 1 and their Binding to P- and E-Selectin
2009
Total synthesis through block glycosylation and selective chemical O-sulfation of tyrosine residues yielded the glycopeptide recognition domain A (X=SO(3) (-)) of the P-selectin glycoprotein ligand 1, in which the terminal sialic acid of the complex hexasaccharide side chain was replaced by (S)-cyclohexyl lactic acid. In binding assays the O-sulfated structure A showed high affinity towards P-selectin, the non-sulfated towards E-selectin.
C-Glycosyl amino acids through hydroboration-cross-coupling of exo-glycals and their application in automated solid-phase synthesis.
2013
O-Glycosylation is one of the most important post-translational modifications of proteins. The attachment of carbohydrates to the peptide backbone influences the conformation as well as the solubility of the conjugates and can even be essential for binding to specific ligands in cell-cell interactions or for active transport over membranes. This makes glycopeptides an interesting class of compounds for medical applications. To enhance the long-term availability of these molecules in vivo, the stabilization of the glycosidic bond between the amino acid residue and the carbohydrate is of interest. The described modular approach affords β-linked C-glycosyl amino acids by a sequence of Petasis …
Hybrid compounds generated by the introduction of a nogalamycin-producing plasmid into Streptomyces argillaceus
2003
The combination of genetic material from different antibiotic-producing organisms is a versatile and ever-expanding approach for the production of novel, hybrid compounds possessing bioactivity. The introduction of a plasmid (pSY21b) derived from Streptomyces nogalater and encoding PKS for nogalamycin production into the host strain S. argillaceus A43 led to the production of three new compounds in addition to the normally produced mithramycin. The new compounds are hybrids in the sense that they share features associated with the genes of both the host and the introduced plasmid. The structural elucidation of the novel compounds relied primarily on NMR spectroscopy, which revealed the thre…
Loss of Contact-Dependent Inhibition of Growth in Chemically Transformed Fibroblasts
1988
The plasma membrane has been recognized as an important regulatory unit of mammalian cells during determination, differentiation, and social behaviour of individual cells within various tissues (1–4). On the molecular level, plasma membrane glycoproteins and glycolipids have been shown to be involved in these processes (1–4). Density-dependent growth of non-transformed cells in vitro has been proposed to be regulated by secreted inhibitory compounds (5–7), by the cell’s shape (8) or by diffusion boundary layers (9). On the other hand, specific cell-cell interactions via cell membrane molecules were found to be of great importance for the contact-dependent inhibition of growth (10–16) and co…
Antitumor Vaccines Based on Synthetic Mucin Glycopeptides
2011
The interest in tumor-associated glycoconjugate antigens was particularly initiated by Springer, who published in 1984 that glycoproteins on the outer cell-membrane of epithelial tumor cells have an altered glycosylation consisting of the Thomsen-Friedenreich (T-) antigen and its precursor the TN-antigen structure (Springer 1984). He and his coworkers also had found that monoclonal antibodies induced with glycoproteins from tumor cell membranes showed cross-reactivity to desialylated glycophorin A. It was concluded from these observations that the T-and TN-glycoproteins on the epithelial tumor cells must be structurally related to asialoglycophorin A (Springer et al. 1983) (Fig. 11.1a). Gly…
Synthetic Antitumor Vaccines Through Coupling of Mucin Glycopeptide Antigens to Proteins
2017
The requirements for coupling reactions of carbohydrate molecules very much depend upon the biological recognition processes that should be investigated and upon the target structures of the desired carbohydrate ligand. If the carbohydrate conjugate itself is the recognized ligand, as for example, the binding site of a P-selectin ligand comprising sialyl-LewisX and a specific peptide sequence, the natural glycoside bond must be installed. A stereoselective and regioselective block glycosylation between a sialyl-LewisX trichloroacetimidate and a partially deprotected Thomsen–Friedenreich antigen derivative was developed to achieve this aim. In contrast, the coupling reactions by which glycop…
Temporal aspects of the O-glycosylation of Saccharomyces cerevisiae mannoproteins
1986
Abstract Cleavage of the O-glycosyl bonds of Saccharomyces cerevisiae cell wall mannoproteins by β-elimination resulted in the release of about 8% of the carbohydrate in the form of mannose and other low molecular weight oligomannosaccharides (mannose to mannopentaose), leaving 92% mannose still covalently linked to the peptide, and suggesting that this alkali-resistant fraction was N-glycosidically linked. At the non-permissive temperature, S. cerevisiae sec mutants accumulated in the cytoplasm mannoproteins with different degrees of O- and N-glycosylation. The glycoproteins of mutant sec 20-1 contained 60% of the carbohydrate linked by N-bonds, the remainder being O-glycosidically linked.…
N-glycosylation efficiency is determined by the distance to the C-terminus and the amino acid preceding an Asn-Ser-Thr sequon
2010
N-glycosylation is the most common and versatile protein modification. In eukaryotic cells, this modification is catalyzed cotranslationally by the enzyme oligosaccharyltransferase, which targets the β-amide of the asparagine in an Asn-Xaa-Ser/Thr consensus sequon (where Xaa is any amino acid but proline) in nascent proteins as they enter the endoplasmic reticulum. Because modification of the glycosylation acceptor site on membrane proteins occurs in a compartment-specific manner, the presence of glycosylation is used to indicate membrane protein topology. Moreover, glycosylation sites can be added to gain topological information. In this study, we explored the determinants of N-glycosylati…
Enzymatic glycosylation of o-glycopeptides
1992
Abstract O-Glycosylation of serine derivatives carried out with N-urethane protected glucosamine yields O-glycopeptides which are regio- and stereoselectively galactosylated with the aid of β-1,4-galactosyltransferase (EC 2.4.1.22).