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Cellular Components of Blood
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The ABO antigens are complex oligosaccharide (carbohydrates) (Figure 51.9). The core antigen is the H antigen, which is a precursor with L-fucose as the terminal sugar. The A antigen is formed when N-acetylgalactosamine is added to the terminal group of the H antigen. The B antigen results when D-galactose is added to the H antigen.
Host Defenses Against Prototypical Intracellular Protozoans, the Leishmania
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
Richard D. Pearson, Mary E. Wilson
A marmose-containing ligand from promastigotes, which is involved in promastigote attachment, has subsequently been isolated from L. mexicana mexicana and other Leishmania species (82-85). Initial examination of promastigote surface proteins by radiolabeling and two-dimensional polyacrylamide gel electrophoresis revealed an abundant polypeptide of molecular weight 63 kD (gp63). Lectin-binding studies indicated that it was a glycoprotein that contained mannose, N-acetyiglucosamine, and N-acetylgalactosamine residues. The gp63 was found to be distributed over the entire promastigote plasmalemma, and anti-gp63 antibodies reduced promastigote binding to macrophages by 65-70% (84). Additional evidence for the involvement of gp63 in parasitemacrophage interactions was provided by studies in which gp63 was incorporated into proteoliposomes. Liposomes containing gp63 were phagocytosed by macrophages, and uptake was inhibited by more than 90% by both anti-gp63 F(ab) fragments and mannan. These results suggest that the abundant gp63 is a ligand for the macrophage mannose/fucose receptor (Fig. 6). Recent studies indicate that this major integral membrane protein is a protease (83). A water-soluble form of the protease is obtained following digestion with the phospholipase C responsible for the release of variant surface glycoprotein from Trypanosoma brucei (83).
Tay-Sachs disease/hexosaminidase A deficiency
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
The disease was first described by Tay [2] in 1881 in an infant in whom a cherry macular spot was associated with delayed development. Sachs [3] defined the clinical entity, which he called a familial amaurotic idiocy [4]. The enzymatic defect was discovered in 1969 by Okada and O'Brien [5]. The deficiency in hexosaminidase A results in a failure to cleave the terminal N-acetylgalactosamine (GalNAc) from the GM2 ganglioside (Figure 88.1). The development of methodology for the rapid, relatively easy quantification of the A isozyme has permitted accurate identification of heterozygous carriers of the gene and prenatal diagnosis, permitting a public health approach to human genetics and the virtual prevention of the birth of affected children in the population at highest risk [6, 7].
Nucleotide binding as an allosteric regulatory mechanism for Akkermansia muciniphila β-N-acetylhexosaminidase Am2136
Published in Gut Microbes, 2022
Chang-Cheng Li, Huan Yi, Yan-Mei Wang, Xin-Yue Tang, Yi-Bo Zhu, Ying-Jie Song, Ning-Lin Zhao, Qin Huang, Xing-Yu Mou, Gui-Hua Luo, Tong-Gen Liu, Gang-Long Yang, Yu-Jiao Zeng, Li-Jie Wang, Hong Tang, Gang Fan, Rui Bao
Oligosaccharide contains different sugar units, due to its wide variety of biological activities, it has potential commercial values in food, pharmaceutical and cosmetic industries.1 β-N-acetylhexosaminidase is one of the most abundant glycosidases and is specific for the hydrolysis of both β-GlcNAc and β-N-acetylgalactosamine (β-GalNAc) units from the non-reducing end of glycan chains.2 Because of the ability to degrade a wide variety of substrates, and the wide resources including bacteria, fungi and arthropods,3,4 various therapeutic and biotechnological applications have been proposed for β-N-acetylhexosaminidase, which include conversion of industrial-scale production of distinct functional carbohydrates and glycan derivatives.5
Recent trends in the development of Toll-like receptor 7/8-targeting therapeutics
Published in Expert Opinion on Drug Discovery, 2021
Xuan Huang, Xiaoyong Zhang, Mengji Lu
Since TLRs share similar regulatory pathways, it is worth investigating downstream signaling as a specific target. Nowadays, the modified derivation and nanoparticles have improved the targeting of drugs for tumors. Studies indicate that R848-loaded β-cyclodextrin nanoparticles can be efficiently delivered to tumor-associated macrophages both in vivo and in vitro, and that in conjunction with checkpoint therapy this results in improved anti-cancer efficacy [136]. Nanoparticle-based delivery can increase target payload with less systemic side effects. So it is possibly applied in cases involving numerous metastatic tumors, unlike image-guided intratumoral injection. Other delivery systems targeting hepatic components, such as N-acetylgalactosamine, are worth considering [137].
Antibodies against aberrant glycans as cancer biomarkers
Published in Expert Review of Molecular Diagnostics, 2019
Anna Blsakova, Filip Kveton, Peter Kasak, Jan Tkac
The most abundant O-glycans are present in mucins, which are “rod-like” proteins heavily decorated with O-glycans. O-glycosylation is a finely tuned enzymatic process integrating more than 50 enzymes, but their cooperation is not fully understood. N-acetylgalactosamine (GalNAc) is bound via – OH to serine and threonine residues. To these core GalNAc structures, various sugars or sulfate esters are afterward added to elongate the glycan structure [21–24]. Since the O-glycosylation process requires finely tuned orchestra of enzymes, defects in organelles in which glycans are synthesized (GA, ER) can cause an incomplete glycosylation with production of unnatural aberrant glycan forms. Folding of glycosyltransferases depends on the activity of a molecular chaperone Cosmc [25] and thus dysfunctional chaperone leads to a drastic decrease of a T-synthase activity [26]. As a result, an expression of aberrant O-glycans such as Tn (Thomsen-nouvelle; GalNAc-O-Ser/Thr), sTn (sialyl Tn; NeuAcα2-6GalNAcα-O-Ser/Thr), and T (Thomsen-Friedenreich; Galβ1-3GalNAcα1-O-Ser/Thr) antigens are produced (Figures 1 and 2) and associated with metastasis and cancer progression [27]. On the other hand, a typical feature of cancerous cells is to synthetize more complex and branched N-glycans, product of aberrant activity of several glycosyltransferases, with their involvement in a signal transduction, cell adhesion, proliferation, etc. [28].