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Biochemical Basis of Cervical Maturation
Published in Gabor Huszar, The Physiology and Biochemistry of the Uterus in Pregnancy and Labor, 2020
The free glycosaminoglycan, hyaluronic acid, and protein-bound glycosaminoglycans, or proteoglycans, are volumetrically the second most abundant component of the extracellular matrix. Glycosaminoglycans are high molecular weight polysaccharides composed of alternating uronic acid and N-acetyl hexosamine residues. The structural details of hyaluronic acid and dermatan sulfate, important glycosaminoglycan components of fibrous connective tissue, are shown in Figure 3 (see Rodén20 for review).
Proteoglycans of the Intervertebral Disc
Published in Peter Ghosh, The Biology of the Intervertebral Disc, 2019
Glycosaminoglycans are heteropoly saccharides composed of repeating disaccharide groups in which an N-acetylated hexosamine is linked by a glycosidic bond to a nitrogen-free monosaccharide, usually a uronic acid. The hexosamine bears a sulfate group, the sole exception to this rule being hyaluronate, where the N-acetylglucosamine does not have an acidic group. The distinctive feature of glycosaminoglycan chains, therefore, is their high fixed charged density, with each disaccharide usually bearing a sulfate and a carboxyl group.
Macromolecular Absorption From The Digestive Tract In Young Vertebrates
Published in Károly Baintner, Intestinal Absorption of Macromolecules and Immune Transmission from Mother to Young, 2019
I discuss separately N-acetyls-hexosaminidase, an enzyme occuring in the distal intestine with an optimum between pH 4.0 and 4.5.738 It occurs in both soluble and particle-bound form in mucosal homogenates. The activity was demonstrated in granules attached to the internal surface of ACS vesicles. After releasing the granules from the membrane in 10 mM CaCl2 solution, they were resolved by gel filtration to N-acetyl-hexosaminidase and to a filamentous protein (“ligatin”), which attaches the enzyme to the membrane.610,1209 The enzyme has both N-acetyl-β-glucosidase and N-acetyl-β-galactosidase activities, but it differs from TV-acetyl-neuraminidase, which splits alpha-glycosidic bonds.1262 N-acetyl-hexosamin-idase is an exoenzyme. It splits hexosamines from the end of carbohydrate chains and disappears at closure time together with the vacuolated cells.742, 738
Advances in oxidative stress in pathogenesis of diabetic kidney disease and efficacy of TCM intervention
Published in Renal Failure, 2023
Xiaoju Ma, Jingru Ma, Tian Leng, Zhongzhu Yuan, Tingting Hu, Qiuyan Liu, Tao Shen
In the glycolysis pathway, approximately 2–5% glucose-6-phosphate (G6P) is converted to fructose-6-phosphate (F6P) and then enters the hexosamine pathway [13]. At states of sustained hyperglycemia, excessive F6P is converted to glucosamine-6-phosphate (GlcN6P) under the catalysis of glutamine fructose-6-phosphate aminotransferase (GFAT), followed by generation of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) with the action of related enzymes. The UDP-GlcNAc is then used as substrate for O-linked N-acetylglucosamine (O-GlcNAc) glycosylation under the catalysis of O-GlcNAc transferase. It was reported that hexosamine can induce endoplasmic reticulum (ER) stress in endothelial cells and macrophages, leading to increased oxidative stress responses. Another study revealed that overexpression of GFAT increases NF-κB promoter activity and TNF-α expression in mesangial cells and stimulates the production of TGF-β1 and PAI-1, inducing inflammatory response, extracellular matrix (ECM) accumulation and diabetic glomerulosclerosis [14].
Breast cancer glycan biomarkers: their link to tumour cell metabolism and their perspectives in clinical practice
Published in Expert Review of Proteomics, 2021
Tomas Bertok, Veronika Pinkova Gajdosova, Aniko Bertokova, Natalia Svecova, Peter Kasak, Jan Tkac
Another branch of glucose metabolism links the aberrant glycosylation to metabolic pathways, namely hexosamine biosynthesis. The product of this pathway, UDP-GlcNAc is also a donor substrate for some reactions catalysed by glycosyltransferases. As shown by Lucena et al., despite an increased glucose uptake in cancer cells, glucose is shunted through hexosamine biosynthesis rather than by an increased glycolysis and pentosephosphate pathway (PPP) for supporting cells with NADPH for lipid synthesis and elimination of reactive oxygen species (ROS) [65,66]. Wild-type p53, for example, negatively affects PPP as well as mTOR (mammalian target of rapamycin regulating cell growth and proliferation during PI3K cell survival pathway), which regulate fatty acid synthesis and also synthesis of a dolichol carrier – a molecule important in the N-glycan biosynthesis [67]. It is worth noting that glycosylation of pyruvate kinase muscle isoform-2 and phosphofruktokinase 1 can reroute the glycolysis more towards PPP [68]. The activity of the rate-limiting enzyme of PPP – glucose-6-phosphate dehydrogenase is dynamically modified by O-linked β-GlcNAc in response to hypoxia, which also provides the precursors for nucleotide synthesis in rapidly dividing cancer cells [69].
The clinical impact of maternal weight on offspring health: lights and shadows in breast milk metabolome
Published in Expert Review of Proteomics, 2021
Flaminia Bardanzellu, Melania Puddu, Diego Giampietro Peroni, Vassilios Fanos
Obesity is recognized as an inflammatory condition closely associated with oxidative stress. The production of ROS induced by pro-inflammatory adipocytokines released by inflamed adipose tissue, which in turn promotes a systemic inflammatory response, seems to be one of the main causes. Some metabolites found different in OW-OB BM could have a role in obesity related oxidative stress: methiltioadenosine, 2-aminobutyrate, glucose-6-phosphate and isothreonic acid could be considered as protective molecules and in this respect their increase in OW-OB BM [115,127], could preserve offspring against chronic inflammation and oxidative stress conditions in the long term. Polyamines also seem to have this role in obesity and their reduction reported by Ali et al. [146] may make the offspring more vulnerable to the consequences of oxidative stress. An increase in N-acetyl-hexosamines could promote inflammation and oxidative stress. A state of persistent inflammation characterizes the adipose tissue of obese subjects and represents a link between the immune and metabolic systems. An altered proportion of different FAs (MUFAs/SFAs, UFAs/SFAs, n-6/n-3 FAs, essential FAs) may have an important role in promoting it.