Analytical Chemistry of Rubins
Karel P. M. Heirwegh, Stanley B. Brown in Bilirubin, 1982
In the light of our present, though limited, knowledge of artificial alterations of rubins during storage and manipulation, the following precautions must be considered in analytical work with rubins. The samples should be shielded from light, manipulations being done in dim, preferably red light. It is recommended to deoxygenate the solvents and, whenever possible, to keep the pigments under an inert atmosphere (nitrogen, argon). Deoxygenation by bubbling of inert gases is likely to facilitate aggregation of supersaturated solutions of bilirubin (IIIα, IXα, and XIIIα) but may affect less, or not at all, aqueous solutions of conjugated bilirubins and polar bilirubin isomers. Autoxidation can be minimized by using ultrapure solvents and reagents. Addition of disodium EDTA (1 to 5 mM) and/or ascorbate (1-5 mM) can be advantageous and frequently permissible. Hydrolysis and acyl-shifting can be avoided by buffering aqueous solutions to pH values below 6. Also, enzymic hydrolysis catalyzed by β-glycosidases present in many biological samples (serum, bile, tissue homogenates, microsomal preparations) can be inhibited by addition of aldonolactones.52,53
Carbohydrate Histochemistry
Joan Gil in Models of Lung Disease, 2020
Loss of staining after digestion with a specific glycosidase yields information about the location of the sugar hydrolyzed by the enzyme. Moreover, lectin histochemical methods make it possible to determine the location of a given sugar with a specific enzyme digestion by imparting lectin staining for the specific penultimate sugar or sugar sequence exposed after the digestion. Most sialoglyco-conjugates, for example, contain galactose or N-acetylgalactosamine penultimate to the terminal sialic acid and gain reactivity for peanut lectin (Steward et al., 1980; Schulte and Spicer, 1985) or a lectin from Dolichos biflorus (Schulte and Spicer, 1985; Schulte et al., 1985a), respectively, after enzymatic removal of the sialic acid. It is conceivable, that a combination of digestion with one or another specific exoglycosidase to remove the terminal sugars in an oligosaccharide chain at a precise location, followed by a battery of lectin procedures to identify the sugar rendered terminal by digestion, could be performed repeatedly to yield information about the sequence of sugars in the oligosaccharide chains.
Section Pretreatment, Epitope Demasking, and Methods for Dealing with Unwanted Staining
Lars-Inge Larsson in Immunocytochemistry: Theory and Practice, 2020
Apart from proteases, some other enzymes have been used for treating sections before immunocytochemistry. These include mixed glycosidases, which Andrews et al.1 reported to reduce unwanted staining of frozen sections. The tissue material used was from mice. Attempts to stain it with mouse monoclonal antibodies were complicated since the second antimouse IgG reagent, as expected, also reacted with endogenous mouse immunoglobulins, present in the interstitial fluid. The authors found that the mixed glycosidase treatment eluted endogenous mouse immunoglobulins and provided for a better background.1 The method would probably not work on tissues fixed in cross-linking fixatives. An alternative approach, applicable to tissues fixed in cross-linking fixatives, and thereby to extractable antigens, would be to use directly labeled (e.g., with fluorochromes, colloidal gold, or biotin) monoclonal antibodies. Much immunoglobulin does occur in interstitial tissues. These can be removed by prolonged washes in saline prior to fixation, but such washing has, of course, applicability only to firmly bound antigens.5
Synthesis of novel tris-chalcones and determination of their inhibition profiles against some metabolic enzymes
Published in Archives of Physiology and Biochemistry, 2021
Serdar Burmaoglu, Ali Osman Yilmaz, M. Fatih Polat, Rüya Kaya, İlhami Gulcin, Oztekin Algul
The α-glycosidase (α-Gly) enzyme (E.C. 3.2.1.20) catalyses the hydrolysis of glycosidic bonds of oligo and polysaccharides to liberate monosaccharides, including glucose monomers. It is released from the intestine cells and is very widely distributed in all organisms (Gulcin and Taslimi 2018, Gulcin et al.2018, Taslimi and Gulcin 2018, Taslimi et al.2018). In humans, α-glycosidase inhibitors (α-GIs) have crucial importance for the controlling of some disorders including hyperglycaemia and type 2 diabetes mellitus (T2DM) (Daryadel et al.2018, Gondolova et al.2018). α-GIs can reduce the uptake of dietary carbohydrates and repress postprandial hyperglycaemia and T2DM. Thus, these α-GIs are endowed with sugar molecules such as moieties competing with the oligosaccharides for binding to the active site of the enzyme (Scozzafava et al.2015, Demir et al.2018, Maharramova et al.2018).
Glycomics of prostate cancer: updates
Published in Expert Review of Proteomics, 2019
Jan Tkac, Tomas Bertok, Michal Hires, Eduard Jane, Lenka Lorencova, Peter Kasak
Glycans are built carbohydrate by carbohydrate and almost every building step is catalyzed by a specific glycosyltransferase and the glycan is simultaneously exposed to the action of glycosidases. The cellular glycome is then the result of genetic expression and the physiological status of the cell. The full picture of cancer development/progression is shown schematically in Figure 1 [16]. Cancer cells with increased sialylation induce the detachment of cancer cells from the neighboring epithelial cells through electrostatic repulsion of negative charges (delivered by sialic acids). Then, the cancerous cells start to interact with the extracellular matrix (ECM) mediated via various types of interactions (Figure 1). The next step is the adhesion of cancer cells to vascular endothelial cells mediated by sialylated glycans (such as SLex) [21], entering the blood circulation and the formation of metastasis (Figure 1).
Absorption, disposition, metabolism and excretion of [14C]mizagliflozin, a novel selective SGLT1 inhibitor, in rats
Published in Xenobiotica, 2019
Hitoshi Ohno, Yasunari Kojima, Hiroshi Harada, Yoshikazu Abe, Takuro Endo, Mamoru Kobayashi
Enzymes with β-glycosidase activity expressed in epithelial cells of the small intestine also play a role in the degradation of glycosides as well. Usually, these enzymes are responsible for the degradation of compounds such as sugar and flavonoid glycosides contained in dietary foods and supplements. Several kinds of β-glycosidase were reported to have β-glucosidase activity including lactase phlorizin hydrolase (LPH), cytosolic β-glycosidase, glucocerebrosidase and so on (Ketudat Cairns & Esen, 2010). Among these, LPH is known to hydrolyse phlorizin that is known to inhibit SGLT1 and SGLT2 non-selectively (Ehrenkranz et al., 2005). Other flavonoid or isoflavonoid glycosides, such as quercetin 3-O-β-glucoside, are also metabolised by LPH (Day et al., 2000; Németh et al., 2003). A recent study demonstrated that broad-specific β-glucosidase metabolise calycosin 7-O-β-glucoside (Shi et al., 2016). It is possible for these enzymes to metabolise mizagliflozin to its aglycone KP232. To summarise, mizagliflozin has a glucoside moiety, which is probably cleaved to form aglycone KP232 by glucosidase in the gut wall and/or that of gut microflora. KP232 is suggested to be absorbed and conjugated with glucuronic acid. KP232 glucuronide can be excreted into bile and then metabolised to KP232 in the gut again. Thus, it is possible that secondary peak occurred in rat is also observed in humans if there is no difference between rats and humans in glucosidase activity of mizagliflozin and also possibly in UDP-glucuronosyltransferase activity and biliary excretion.