Glycosidase Mechanisms (2023)


Only in the last two years has the true catalytic power of glycosidases been fully revealed through the studies of Wolfenden on the spontaneous hydrolysis of polysaccharides [1]. Rate improvements up to 1017-fold are typical and count glycosidases among the most powerful enzymes. In the last two to three years, the major mechanistic advances have been in the structural analysis of enzyme-ligand complexes, elucidation and exploration of variations in standard mechanisms, modification of mechanisms and specificity by site-directed mutagenesis, etc. and the generation of new ones Inhibitors. After a brief introduction, this paper focuses mainly on recent developments in these areas. More detailed reports can be found in a number of recent reviews 2, 3, 4, 5, 6, 7, 8, 9, 10.

The sequence-based classification of glycosidases remains an extremely valuable tool in our understanding of structure/function relationships, and the number of families continues to grow, most recently around 80. This information is currently available on a well-designed website (∼pedro/CAZY/db.html) 11, 12, which was recently extended to include glycosyltransferases, polysaccharide lyases, and carbohydrate esterases, as well as binding modules. Three-dimensional structures are now available for representatives of around 30 of these 80 families. New family structures published since the last comprehensive list [7] include families 3 [13], 47 [14], 48 [15] and 77 [16].

There are two possible stereochemical outcomes for the hydrolysis of glycosidic bonds: inversion or retention of anomeric configuration. Both mechanisms (Figure 1) involve transition states similar to the oxacarbenium ions and a pair of carboxylic acids in the active site. For inverting glycosidases, these two residues are on average about 10 Å (+/− 2 Å) apart 5 , 17 and the reaction proceeds via a simple elimination mechanism in which one carboxylic acid acts as the general base and the other as the general acid base (Figure 1a ). In retention enzymes, the two carboxylic acid residues are about 5.5 Å apart 5, 17 and the reaction proceeds by a double displacement mechanism (Figure 1b).

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Mechanistic insights from structural studies

A particularly telling account is Davies'et al. [18••] showing the X-ray crystal structures of the four stable states along the enzyme reaction coordinate of retainer family 5 β-glycosidase. These were native, substrate-bound, covalent intermediates and product complexes of Cel5ABacillus agaradherens. In other cases, 19, 20 the sugar at the -1 subsite is distorted, as can be seen for the bound substrate (Michaelis complex).1S3skew-boot conformation. It can be

Mechanical anomalies

A variation in the general enzyme retention mechanism has been demonstrated forN-Acetyl-β-hexosaminidase belonging to families 18 and 20. In these enzymes the substrateN-Acetyl group takes the place of the enzymatic nucleophile, attacks the anomeric center, and forms an oxazolinium intermediate as shown in Figure 3. Such a mechanism is well known for acid catalyzed hydrolysisN-acetylglucosaminide [31] and was previously considered for enzymes [7]. consistent

Mechanisms of formation and peculiarities of formation by mutagenesis

Techniques for identifying important active site residues based on detailed kinetic analysis of mutants modified at these positions (see [4]) have been applied to several glycosidases. Thus, the acid/base residue in galactanase A formsPseudomonas fluorescenswas identified by studies with substrates with different leaving group abilities [42], while the identity of the nucleophile in the active site of β-glycosidase differed fromSulfolobus solfataricuswas confirmed by studies on as Glu387

Insights into Inhibitors

The already mentioned high catalytic capacity of glycosidases requires very high transition‐state affinities of the order of 10−22M [1]. This suggests that very tightly bound analogues of transition-state inhibitors of glycosidases are possible, with potential as therapeutic agents. Interest in glycosidase inhibitors as therapeutics has increased in recent years with the successful commercialization of α-amylase-acarbose inhibitor for glycemic control and sialidase


Structural studies of complexes of different types have provided important mechanistic insights into this class of enzymes over the past two to three years and are expected to continue to contribute, especially in studies of enzyme/inhibitor complexes. While site-directed mutagenesis will continue to be an important tool in studying the role of individual side chains, directed evolution will play an important role in creating enzymes with new specificities and possibly even new mechanisms.


The authors thank the Natural Sciences and Engineering Research Council of Canada and the Network of Centers of Excellence for Protein Engineering Canada for financial support.

References and recommended reading

Contributions of particular interest published during the annual review period will be highlighted as follows:

  • • of special interest

  • •• of exceptional interest

Cited by (441)

  • Mechanism-based design and synthesis of exocyclic cyclitol aziridines as potential glycosidase inactivators

    2023, European Journal of Organic Chemistry

    (Video) Glycoside Hydrolysis with Glycosidases

    Cyclopelitol aziridines have found wide application as mechanism-based covalent and irreversible inhibitors of retention glycosidases. These compounds, as well as their parent cyclophellitol (a natural product that retains the β-glucosidase inactivator), utilize the mechanism of action of retention of glycosidases, which process their substrate by forming a transient covalent intermediate. In contrast, inverting glycosidases, another large family of glycosyl hydrolases, do not utilize such a covalent intermediate, and thus useful scaffolds for mechanism-based inhibitor design have yet to be discovered. In this work, we investigate the chemical processes that enable the assembly of cyclitol aziridine, in which an aziridine electrophile is exocyclically bound, more distal than the anomeric carbon—and thus supposedly closer to the nucleophile of the inverting glycosidase active site. The developed chemistry enabled the synthesis of a directed library of diverse contentsN‐substituted α‐ and β‐glucopyranose‐configured cyclitol aziridines for future evaluation as inhibitors or inactivators of α‐ and β‐glucosidases.

  • Improving the catalytic activity of β-glucosidase from Coniophora puteana by semirational design for efficient degradation of biomass cellulose

    2023, Enzyme and Microbial Technology

    To improve the degradation activity of β-glucosidase (CpBgl).Coniophora putianaa structural change was made. The enzyme activity of the CpBgl-Q20C and CpBgl-A240S mutants increased by 65.75% and 58.58%, respectively. These mutants showed maximal activity under the same conditions as wild-type CpBgl (65 °C and pH 5.0), slightly improved stability compared to wild-type, and significantly improved activity in the presence of Mn2+I live2+. TheVmaxCpBgl-Q20C and CpBgl-A240S increased from 81.34 μmol/mg/min in wild type to 138.18 and 125.14 μmol/mg/min, respectively, and the efficiency of catalysis (kCat/KM) CpBgl-Q20C (335,79 Min.)−1/mM) i CpBgl-A240S (281,51 min−1/mM) was significantly improved compared to wild type (149.12 min.).−1/mM). When the CpBgl-Q20C mutant was used in the practical degradation of various biomasses, the yields of glucose in filter paper, corn cob residue and fungal mycelium residue increased by 17.68%, 25.10% and 20.37%, respectively. In this work, the spatial positions of mutation residues in the architecture of CpBgl and their unique role in enzyme and substrate binding and catalytic efficiency were investigated. These results laid the groundwork for the development of other glycoside hydrolases and the industrial biodegradation of cellulosic biomass in nature.

  • The role and importance of solvents for the fractionation of lignocellulosic biomass

    2023, Bioresource Technology

    Lignocellulosic biomass is one of the most important renewable materials replacing carbon-based fossil resources. Solvent-based fractionation is a promising way to fractionate biomass into its main components. Processing is determined by the properties of the solvent systems used. This Review sheds light on the factors that control the solubilization and potential reactivity of the chemical structures present in lignocellulose and demonstrates how a proper understanding of the underlying mechanisms and solute–solvent interactions aids in the selection of appropriate systems for specific fractionation needs. The structural and chemical differences between carbohydrate and lignin-based structural polymers require very different abilities of the solvents to induce and ultimately stabilize conformational changes and activate the resulting bonds that cleave other active components. Considering possible depolymerization events during the dissolution and energetic aspects of the dissolution process with regard to the contribution of polymer functionalities allow to map the suitability of solvents for biomass fractionation.

  • Spirocyclopropyl Carbohydrates: Synthesis and Applications

    2023, Tetraeder

    This review article highlights selected advances in the synthesis of spirocyclopropyl carbohydrates and nucleosides. The cyclopropyl moiety is a versatile functional group that has been shown to facilitate the preparation of a variety of value-added compounds, including β-C-glycosyl amino acids, spiroketals, and dioxaspirolactones. In addition, this review also describes the use of spirocyclopropyl carbohydrates as glycomimetic inhibitors of biologically relevant enzymes, including glycosidases, protein methyltransferase, kinase, and viral polymerases.

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  • The structure of the glycoside-hydrolase-iminosugar complex of the lichenase family 5 provides insight into the active site

    2023, Biochemistry

    TmCel5B is a lichenase belonging to the glycoside hydrolase 5 family of subfamily 36 (GH5_36). To gain insight into the active site of this multifunctional endoglycanase subfamily, we determined the crystal structure of TmCel5B in complex with the iminosugar 1-deoxynojiromycin (DNJ). DNJ is attached to the -1 subsite and forms a network of noncovalent interactions with the acid/base residue Glu139, the nucleophile Glu259, and other residues conserved in the GH5 family. The catalytic site displayed a Glu-Arg-Glu triad of catalytic glutamates found only in the GH5_36 subfamily. A structural comparison of the active sites of GH5_36 homologues revealed divergent residues and loop regions that are likely molecular determinants of homologue-specific properties. Furthermore, a comparative analysis of the binding mode of iminocyclitol complexes of GH5 homologues revealed the structural basis of their binding to GH5 glycosidase, where the binding site of subsites, ligand interactions with specific conserved residues, and electrostatic interactions of catalytic glutamates with ring nitrogen are crucial.

  • Structural insight into a putative glycoside hydrolase of the β-1,4-xylosidase (PsGH43F) family 43 from Pseudopedobacter saltans

    2022, International Journal of Biological Macromolecules

    Structural and conformational insights into a putative β-1,4-xylosidase (P.sGH43F) family glycoside hydrolase 43 fromPseudopedobacter saltanswere examined by computer analysis and circular dichroism (CD) analysis.P.sGH43F has been cloned and expressedE coliBL21 (DE3) cells and the purified enzyme showed a size of ~50 kDa by SDS-PAGE analysis. Alignment of multiple sequencesP.sThe sequence of GH43F, followed by overlaying the modeled structure with homologous structures, revealed the presence of three conserved catalytic amino acid residues, Asp33, Asp149 and Glu212. Secondary structure analysis by CD revealed 2.72% α-helix and 36.06% β-strands. Homology modeled structureP.sGH43F showed a five-sheet β-propeller fold for the catalytic module at the N-terminus and a β-sandwich structure for CBM6 at the C-terminus. The Ramachandran plot showed 99.5% of the residues in the allowable regions. MD simulationP.sGH43F showed the compactness and stability of the structure. Molecular Docking StudiesP.sGH43F with xylo-oligosaccharides showed its maximum binding affinity for xylobiose. MD simulationP.sThe GH43F xylobiose complex confirmed increased structural and conformational stability in the presence of the substrate. Hydrodynamic diameter analysisP.sGH43F by DLS ranged from 0.25-0.28 μm.

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    This article reviews recent developments in the development and application of activity-based probes (ABPs) for glycosidases, with a focus on the various enzymes involved in glucosylceramide metabolism in humans. Various catalytic reaction mechanisms involved in the inversion and retention of glycosidases have been described. Understanding catalysis at the molecular level has led to the development of different types of ABPs for glycosidases. Such compounds range from (1) transition-state mimics labeled with reactive moieties that bind to the target active site, thereby forming covalent bonds in or near the catalytic pocket in a relatively nonspecific manner, to (2) enzyme substrates that encapsulate the catalytic From glycosidase targets to release highly reactive species within the enzyme active site to (3) probes based on mechanism-based covalent and irreversible glycosidase inhibitors. Some applications of activity-based glycosidase probes in biochemical and biological research are discussed, including the specific quantitative visualization of active enzyme moleculesin vitroIliveand as strategies to unambiguously identify catalytic residues in glycosidasesin vitro.

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    Characterization of two families of 36 α-galactosidase glycoside hydrolases: novel transglycosylation activity, lead-zinc tolerance, alkaline and multiple pH optima, and low temperature activity

    Food Chemistry, Vol. 194, 2016, pp. 156-166

    Two α-Galactosidases, AgaAJB07 byMesorhizobiumand AgaAHJG4 fromStreptomyces, are expressed inEscherichia coli. Recombinant AgaAJB07 showed an increase of 2.9-fold and 22.6-foldkCatwith a simultaneous increase of 2.3-fold and 16.3-foldKMin the presence of 0.5 mM ZnSO4i 30,0 mM Pb(CH3GUGUTATI)2, that is. Recombinant AgaAHJG4 appeared to show optimal activity at pH 8.0 in McIlvaine or Tris-HCl buffer and 9.5 in glycine-NaOH or HCl-Borax-NaOH buffer, activity retention of 23.6% and 43.2% when tested at 10 or 20 °C and a half-life of about 2 minutes at 50 °C. activation energies forstr-Nitrophenyl-a-D- Hydrolysis of galactopyranoside by AgaAJB07 and AgaAHJG4 was 71.9 ± 0.8 and 48.2 ± 2.0 kJmol−1, that is. Both AgaAJB07 and AgaAHJG4 showed transglycosylation activity, but required different acceptors and produced different compounds. In addition, possible factors for the alkaline and multiple pH optima as well as the adaptations of AgaAHJG4 to low temperatures have been suggested.

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    Is mutation of the acid/base catalyst moiety in β-D-mannosidase DtMan from Dictyoglomus thermophilum sufficient to confer thioglycoligase activity?

    Biochemistry, Volume 137, 2017, pp. 190-196 (view, other).

    Glycoside hydrolases can be converted to thioglycoligase by mutation of the acid/base catalytic carboxylate residue. The creation of these mutants proved valuableS-glycoside, but few examples in the literature describe the potent action of thioglycoligase and even fewer describe the underlying molecular mechanism.Dthuman, family GH2 β-D-mannosidase from thermophilesDictyoglomus thermophilumwas cloned and expressed inE coli.The recombinant protein is highly specific for β-D-mannosides and exhibits effective catalytic constants associated with thermostability. However, seven variants carrying a mutant acid/base residue could not be converted into efficient thioligases. crystal structure ofDtMan Glu425Cys mutant and molecular modeling calculations showed that in contrast to other reported GH2 thioligases, the accessibility of the thiol acceptor active site can be compromised by the rigidity of the input loop. This structural feature might explain whyDtHuman mutants do not show thioglycoligase activity.

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    Structural insights into β-glucosidase transglycosylation based on biochemical, structural, and computational analysis of two GH1 enzymes from Trichoderma harzianum

    New Biotechnology, Volume 40, Part B, 2018, p. 218-227

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    β-Glucosidases are glycoside hydrolases that can cleave small and soluble substrates to generate monosaccharides. These enzymes are divided into the GH1, GH2, GH3, GH5, GH9, GH30 and GH116 families, with GH1 and GH3 being the most relevant families of characterized enzymes to date. A recent transcriptomic analysis of a fungusTrichoderma harzianum, known for its increased β-glucosidase activity compared toTrichoderma reesei, discovered two enzymes from the GH1 family with high expression. Here we report the cloning, recombinant expression, purification, and crystallization of these enzymes, ThBgl1 and ThBgl2. A careful study of the enzymatic activity of these enzymes surprisingly revealed a significant difference between them despite sequence similarity (53%). ThBgl1 has an increased tendency to catalyze the transglycosylation reaction, while ThBgl2 functions more as a hydrolyzing enzyme. A detailed comparison of their crystal structures and analysis of molecular dynamics simulations reveal the presence of the aspartic acid residue N186 in ThBgl2, which is replaced by phenylalanine F180 in ThBgl1. This single amino acid change appears to be sufficient to create a polar environment, culminating in an increased availability of water molecules in ThBgl2 compared to ThBgl1, thus conferring more hydrolytic character on the former enzyme.

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    Characterization of a family of thermostable glycoside hydrolases 36 α-galactosidases from Caldicellulosiruptor bescii

    Journal of Bioscience and Bioengineering, Band 124, Nummer 3, 2017, p. 289-295

    A putative gene cluster involved in the degradation of raffinose family oligosaccharides (RFOs) was identified inCaldicellulosiruptor bescii. Within the cluster, a gene encoding a putative α-galactosidase (CbAga36) was cloned and expressedEscherichia coli.Size exclusion chromatography of purified rCbAga36 showed that the native form was a tetramer. Its primary sequence was similar to that of the glycoside hydrolase family 36. Purified recombinant CbAga36 (rCbAga36) was optimally active at pH 5.0 and 70°C and had a half-life of 15 hours and 10 hours at 70°C and 80°C, respectively. . rCbAga36 showed high activity with artificial substrate (str-Nitrofenil α-D-Galactopyranosid,strNPαGal) exposure lowerKMand biggerkCatbut natural substrates such as melibiose and raffinose. Although rCbAga36 showed preferential activity in the hydrolysis of RFOs such as raffinose and stachyose, it did not degrade polymeric galactomannans. Our results suggest that CbAga36 may play a role in the degradation of RFO, which is transported via a transporter into the cytoplasm to galactose, which is further used as an energy sourceC. Animals. Furthermore, due to its ability to synthesize new oligosaccharides through transglycosylation, this enzyme is potentially useful for the production of food oligosaccharides with a new function.

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    Site-specific α-glycosylation of hydroxyflavones and hydroxyflavanones by amylosucrase from Deinococcus geothermalis

    Enzyme and Microbial Technology, Band 129, 2019, Artikel 109361

    Amylosucrase (ASase) is a unique multifunctional enzyme that exhibits transglycosylation activity. In this study, the specificity of ASase transglycosylation activity was evaluated using multiple hydroxyflavones (HFVO) and hydroxyflavanones (HFVA). Our results show that the 3-OH and 7-OH positions of mono-HFVO and -HFVA are resistant to transglycosylationDeinococcus geothermalisASase (DGAS), while the 6-OH and 4′-OH positions of mono-HFVO and -HFVA show relatively strong transglycosylation reactivity with glucose donors released from sucrose by DGAS. In particular, the 6-OH position is significantly more reactive (54 times higher k).Cat) from the 4'-OH position in HFVO and HFVA. In addition, transglycosylation reactions with di- and tri-HFVO and HFVA were also examined and observed to show results similar to those observed for mono-HFVO and -HFVA molecules. The pH of the reaction affects the reactivity of certain hydroxyl residues, suggesting that the pKa values ​​of hydroxyl groups may be key factors in transglycosylation reactions. These observations help us to understand the specificity of ASase transglycosylation activity and to predict the transglycosylation products of flavonoids.

Copyright © 2000 Elsevier Science Ltd. All rights reserved.


What is the mechanism of Glycosidase? ›

Glycosidases which hydrolyses their substrates with net retention of anomeric configuration (retaining enzymes) do so via a double-displacement mechanism in which a covalent glycosyl-enzyme is formed and hydrolysed with acid/base catalytic assistance via oxocarbenium ion-like transition states.

What is the mechanism of retaining glycosidases? ›

Retaining glycosidases operate through a two-step mechanism, with each step resulting in inversion, for a net retention of stereochemistry. Again, two residues are involved, which are usually enzyme-borne carboxylates. One acts as a nucleophile and the other as an acid/base.

What is the mechanism of glycoside hydrolysis? ›

Glycoside hydrolases are enzymes that catalyze the hydrolysis of the glycosidic linkage of glycosides, leading to the formation of a sugar hemiacetal or hemiketal and the corresponding free aglycon. Glycoside hydrolases are also referred to as glycosidases, and sometimes also as glycosyl hydrolases.

What type of enzyme is glycosidase? ›

Glycosidases are enzymes that normally break glycosidic bonds during glycoprocessing or catabolism of oligosaccharides, but by placing glycosidases under certain controlled reaction conditions they can be utilized to form, rather than break, glycosidic bonds.

What is an example of a glycosidase? ›

Other examples of glycosidases are lactase, O-GlcNAcase, amylase, hyaluronidase, sucrose, and maltase.

What is the use of glycosidase? ›

Glycosidases are involved in the biosynthesis of the oligosaccharide chains and quality control mechanisms in the endoplasmic reticulum of the N-linked glycoproteins.

What is the mechanism of glycosidic linkage? ›

A glycosidic bond (also known as glycosidic linkage)is created when the hemiacetal of a saccharide (or a molecule generated from a saccharide) reacts with the hydroxyl group of another substance, such as alcohol. Only sugars with the cyclic forms have an anomeric carbon and are capable of forming a glycosidic link.

What happens in glycoside formation? ›

Glycoside is a compound formed from a simple sugar and another compound by replacement of a hydroxyl group in the sugar molecule. Glycosides found in plants include some pharmacologically important products.

What is glycoside metabolic process? ›

glycoside metabolic process Gene Ontology Term (GO:0016137) Definition: The chemical reactions and pathways involving glycosides, compounds in which a glycosyl group is substituted into a hydroxyl, thiol or selenol group in another compound.

What is the mechanism of hydrolysis of glycosidic bond? ›

The hydrolysis of glycosidic linkages occurs through the addition of a water molecule and the action of a catalyst. Different linkages require specific enzymes for hydrolysis to break the bond, allowing monosaccharides to be released for metabolism.

What is the mechanism of action of glycoside inhibitors? ›

Mechanism of Action

Alpha-glucosidase inhibitors inhibit the absorption of carbohydrates from the small intestine. They competitively inhibit enzymes that convert complex non-absorbable carbohydrates into simple absorbable carbohydrates. These enzymes include glucoamylase, sucrase, maltase, and isomaltase.

Does hydrolysis break glycosidic bonds? ›

2 Catalytic Reaction Mechanism of Glycosidases. Glycosidases hydrolyze the glycosidic bond between the glycon and the aglycon via a reaction that results in inversion or retention of the anomeric stereochemistry in the glycon, a mechanism first proposed in 1953 by Daniel E. Koshland, Jr.

What do you mean by glycosidase? ›

glycosidase. noun. gly·​co·​si·​dase glī-ˈkō-sə-ˌdās, -zə-ˌdāz. : an enzyme that catalyzes the hydrolysis of a bond joining a sugar of a glycoside to an alcohol or another sugar unit.

What are the different types of glycosidases? ›

There are two types of glycosidases: (i) exo-glycosidases that release a single monosaccharide from the nonreducing terminus of an oligosaccharide; and (ii) endo-glycosidases that cleave internal glycosidic bonds.

What is the substrate of glycosidases? ›

The enzyme hydrolysed a large number of beta-linked glycoside dimers and oligomers; chromogenic beta-glucosides and beta-fucosides are the preferred substrates, and kinetic analysis indicated that they bind to a common catalytic site.

What is an example of glycoside in pharmacology? ›

Some examples include anthraquinone, coumarin, cyanogens (cyanohydrin), flavonoids, glucosinolates (or thioglycosides), phenols, steroidal, terpenoids, and saponins.

What is the function of glycoside hydrolase? ›

The majority of these plant glycoside hydrolases are involved in cell wall polysaccharide metabolism. Other functions include their participation in the biosynthesis and remodulation of glycans, mobilization of energy, defence, symbiosis, signalling, secondary plant metabolism and metabolism of glycolipids.

What is the difference between glycosidase and glycosylases? ›

Glycosylases (EC 3.2) are enzymes that hydrolyze glycosyl compounds. They are a type of hydrolase (EC 3). In turn, glycosylases are divided into two groups: glycosidases—enzymes that hydrolyze O- and S-glycosyl compounds (EC 3.2. 1) -- and enzymes that hydrolyze N-glycosyl compounds (EC 3.2.

What are 4-glycosidic linkages? ›

A 1,4-glycosidic bond is a covalent bond between the -OH group on carbon 1 of one sugar and the -OH group on carbon 4 of another sugar. This is a condensation reaction as a molecule of water is released. It can be broken by consuming a molecule of water in a hydrolysis reaction.

What is a glycosidic linkage in simple terms? ›

Glycosidic linkage refers to the linkage formed between two monosaccharide units through an oxygen atom by the loss of a water molecule. For example, in a sucrose molecule, two monosaccharide units, ∝-glucose and β-fructose, are joined together by a glycosidic linkage.

How is glycoside formed from glucose? ›

Acetal derivatives formed when a monosaccharide reacts with an alcohol in the presence of an acid catalyst are called glycosides. This reaction is illustrated for glucose and methanol in the diagram below.

How are glycosides formed in glucose? ›

Glycosides are formed when the anomeric (hemiac-etal or hemiketal) hydroxyl group of a monosaccharide undergoes condensation with the hydroxyl group of a second molecule, with the elimination of water.

What is the general method of glycoside? ›

The general method of extraction of glycosides is outlined here. The drug containing glycoside is finely powdered and the powder is extracted by continuous hot percolation using soxhlet apparatus with alcohol as solvent. During this process, various enzymes present in plant parts are also deactivated due to heating.

What are the functions of glycosides in the human body? ›

They are used in the treatment of heart diseases e.g. congestive heart failure (historically as now recognised does not improve survivability; other agents are now preferred] and arrhythmia.

What is the difference between glucose and glycoside? ›

In glucoside, glucose is attached to the non-sugar group via a glycosidic bond, while in glycoside, a sugar group like monosaccharide, disaccharide, or oligosaccharide is attached to the non-sugar group via a glycosidic bond. So, this is the key difference between glucoside and glycoside.

What do glycosides do in human? ›

Cardiac glycosides are medicines for treating heart failure and certain irregular heartbeats. They are one of several classes of drugs used to treat the heart and related conditions.

What enzyme breaks glycosidic bonds? ›

The enzyme amylase can break glycosidic linkages between glucose ...

How is glycosidic bond formed in glucose? ›

Glycosidic bond is a condensation reaction between two sugar units, where the H- group from one sugar interacts with the -OH group on another to release water and link the sugar units together to form a polysaccharide.

What are the two types of glycosidic bonds? ›

There are are two types of glycosidic bonds - 1,4 alpha and 1,4 beta glycosidic bonds. 1,4 alpha glycosidic bonds are formed when the OH on the carbon-1 is below the glucose ring; while 1,4 beta glycosidic bonds are formed when the OH is above the plane.

What effect do glycosides have on blood pressure? ›

') that cardiac glycosides such as ouabain and digoxin increase the sodium and calcium content of smooth muscle cells, so inducing arterial vasoconstriction and a rise in blood pressure.

What is the antidote for glycosides? ›

Digoxin immune FAB is a specific antidote that may be effective in some forms of cardiac glycoside plant poisoning. This agent has been used successfully in patients with oleander toxicity and may cross-react with other cardiac glycosides.

What are the main mechanisms of action of digoxin? ›

Mechanism of Action

Digoxin induces an increase in intracellular sodium that will drive an influx of calcium in the heart and cause an increase in contractility. Cardiac output increases with a subsequent decrease in ventricular filling pressures.

What do glycosides yield on hydrolysis? ›

Some simple glycosides such as β methyl-2,3,4,6-tetra-O-methyl-D-glucopyranose are hydrolyzed under diluted HCl conditions to yield a hydroxy-2,3,4,6-tetra-O- methyl-D-glucopyranose. Likewise β ethyl-glucopyranose is hydrolyzed to a mix- ture of anomers (Figure 7.1).

What reaction breaks the glycosidic bonds by adding water to form two monosaccharides? ›

We now know that the type of reaction that involves the addition of water to break the bond between two monosaccharides is called a hydrolysis reaction.

What bonds break during hydrolysis? ›

During hydrolysis, covalent bonds between monomers break, which allows for the breaking down of polymers.

Is lysozyme a glycosidase? ›

One of the polysaccharide-degrading enzymes is lysozyme (E.C 3.2. 1.17), and its structure was first illuminated in the 1960s by X-ray crystallography (12). Lysozyme is a glycosidase (a type of murein hydrolases) with a molecular weight of almost 11–22 kDa and the pH of isoelectric point of approximately 9.5–11 (15).

What are the three types of glycosides? ›

There are three types of glycosidic linkages, namely, O-glycosidic linkages, N-glycosidic linkages, and C-glycosidic linkages. In the case of C-linkages, the glycoside is resistant to acid hydrolysis.

What are the sources of glycosides? ›

Many glycosides occur in plants, often as flower and fruit pigments; for example, anthocyanins. Various medicines, condiments, and dyes from plants occur as glycosides; of great value are the heart-stimulating glycosides of Digitalis and Strophanthus, members of a group known as cardiac glycosides.

How does protease break down protein? ›

Proteases are enzymes that break the peptide bond that joins amino acids together in proteins. They are examples of hydrolases, enzymes that break a chemical bond by the addition of a water molecule.

What is the difference between alpha and beta glucosidase? ›

α-Glucosidase is a carbohydrate-hydrolase that releases α-glucose as opposed to β-glucose. β-Glucose residues can be released by glucoamylase, a functionally similar enzyme. The substrate selectivity of α-glucosidase is due to subsite affinities of the enzyme's active site.

What is a retaining mechanism? ›

(a) The retaining mechanism, in which the glycosidic oxygen is protonated by the acid catalyst (AH) and nucleophilic assistance to aglycon departure is provided by the base B.

What is the mechanism of glycosidic bond? ›

Glycosidic bonds are the covalent chemical bonds that link ring-shaped sugar molecules to other molecules. They form by a condensation reaction between an alcohol or amine of one molecule and the anomeric carbon of the sugar and, therefore, may be O-linked or N-linked.

What is the mechanism of glycosyltransferase? ›


An active-site side chain serves as a base catalyst that deprotonates the incoming nucleophile of the acceptor, facilitating direct SN2-like displacement of the activated (substituted) phosphate leaving group (Figure 4a).

What is the mechanism of glycosyl transferases? ›

Glycosyltransferases (GTs) catalyze the transfer of a sugar moiety from an activated donor sugar onto saccharide and nonsaccharide acceptors. A sequence-based classification spreads GTs in many families thus reflecting the variety of molecules that can be used as acceptors.

What is the function of glycosylase? ›

DNA glycosylases play a key role in the elimination of such DNA lesions; they recognize and excise damaged bases, thereby initiating a repair process that restores the regular DNA structure with high accuracy.

What are the two types of glycosidic linkages? ›

There are are two types of glycosidic bonds - 1,4 alpha and 1,4 beta glycosidic bonds. 1,4 alpha glycosidic bonds are formed when the OH on the carbon-1 is below the glucose ring; while 1,4 beta glycosidic bonds are formed when the OH is above the plane.

What chemical reaction does glycosyltransferase catalyze? ›

Glycosyltransferases catalyze the formation of a glycosidic bond between an unactivated acceptor monosaccharide or aglycon and an activated sugar donor [26] to a di-, oligo-, polysaccharide [27], lipo(poly)saccharide [28] or peptidoglycan [29].

What is the function of glycosyltransferase in bacteria? ›

Glycosyltransferases (GTs) are a large family of enzymes that catalyze the transfer of activated sugars to a variety of acceptor molecules; they are important in all domains of life for the biosynthesis of complex carbohydrates and glycoconjugates.

What are the uses of glycosyltransferase? ›

Uses. Glycosyltransferases have been widely used in both the targeted synthesis of specific glycoconjugates as well as the synthesis of differentially glycosylated libraries of drugs, biological probes or natural products in the context of drug discovery and drug development (a process known as glycorandomization).

What is the difference between glycosylases and glycosidases? ›

Glycosylases (EC 3.2) are enzymes that hydrolyze glycosyl compounds. They are a type of hydrolase (EC 3). In turn, glycosylases are divided into two groups: glycosidases—enzymes that hydrolyze O- and S-glycosyl compounds (EC 3.2. 1) -- and enzymes that hydrolyze N-glycosyl compounds (EC 3.2.

What is the role of the DNA glycosylase enzyme quizlet? ›

DNA glycosylase is involved in base-excision repair. It removes the affected base by cleaving the N-glycosyl bond. This leads to either an Apurinic site or Apyrimidine site (No longer has the base attached to sugar/phosphate group).

Which bonds are cleaved by glycosylase? ›

Bifunctional glycosylases cleave the N-glycosidic bond using an amine nucleophile of the enzyme, giving a Schiff base (imine) intermediate that facilitates a second enzymatic activity, cleavage of the phosphodiester backbone on the 3' side of the lesion (β-elimination).


1. Alpha Glycosidase
(Sperm 360)
2. Types of Hydrolase Enzymes w/ Mechanisms (peptidase, nuclease, lipase, glycosylase, phosphatase)
(Science Simplified)
3. Glycogen metabolism
(Osmosis from Elsevier)
4. Medical vocabulary: What does Uracil-DNA Glycosidase mean
(botcaster bot)
5. QM/MM Best Practice: Modeling catalytic mechanisms in carbohydrate-active enzymes with QM/MM methods
(BioExcel CoE)
6. Lecture 9 - Metabolic Regulation
(Lewis Research Group LRG)


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