Endoglycosidase
Encyclopedia
An Endoglycosidase is an enzyme
that releases oligosaccharide
s from glycoprotein
s or glycolipid
s. Or it merely cleaves polysaccharide chains between residues that are not the terminal residue, although releasing oligosaccharides from conjugated protein and lipid molecules is more common.
It breaks the glycosidic bonds between two sugar monomer
in the polymer
. It is different from exoglycosidase
that it does not do so at the terminal residue. Hence, it is used to release long carbohydrates from conjugated molecules. If an exoglycosidase were used, every monomer in the polymer would have to be removed, one by one from the chain, taking a long time. An endoglycosidase cleaves, giving a polymeric product.
PROTEIN-x1-x2-x3-x4-x5-x6-x7-x8-x9-x10-x11-...-xn
Both mechanisms exhibit the same distance between the proton donor and the glycosidic oxygen, situating the proton donor close enough to the glycosidic oxygen for hydrogen bonding.(1) It is the distance between the nucleophile and the anomeric carbon where the two mechanisms begin to diverge. Because the inversion mechanism must accommodate enough space for the water molecule, the nucleophile is situated further away from the anomeric carbon. In the inversion mechanism, this distance is only 5.5 angstroms but increases to 10 angstroms in the retention mechanism. Furthermore, the inversion mechanism was found to proceed through a single displacement mechanism involving an oxocarbenium ion-like transition state. Due to the retention mechanism’s proximity between the two carboxyl groups, it goes through a double displacement mechanism that produces a covalent glycosyl-enzyme intermediate.(2-3)
A exoglycosidase would remove each carbohydrate monomer (x) one by one from the end, starting at xn, whereas and endogylcosidase can cut at any glycosidic bond (-) and may cleave after a signature 'link oligosaccharide' that links certain carbohydrates to certain proteins.
For more information on linkages to proteins see O- and N- linked glycoproteins.
Refer to the Handbook of Endoglycosidases and Glycoamidases http://www.amazon.com/dp/084933618X by Noriko Takahashi
Endoglycosidases also has potential application in fighting autoimmune diseases such as arthritis and systemic lupus erythematosus. In 2008, a team of researchers demonstrated that injection of endgoglycosidase S “efficiently removes the IgG-associated sugar domain in vivo and interferes with autoantibody-mediated proinflammatory processes in a variety of autoimmune models.”(5) Clearly the manipulation and mutation of this enzyme holds great promise for being able to fight a variety of diseases in the body.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that releases oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
s from glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
s or glycolipid
Glycolipid
Glycolipids are lipids with a carbohydrate attached. Their role is to provide energy and also serve as markers for cellular recognition.-Metabolism:...
s. Or it merely cleaves polysaccharide chains between residues that are not the terminal residue, although releasing oligosaccharides from conjugated protein and lipid molecules is more common.
It breaks the glycosidic bonds between two sugar monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
in the polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
. It is different from exoglycosidase
Exoglycosidase
A exoglycosidase is a glycoside hydrolase enzyme which breaks the glycosidic bonds at the terminal residue....
that it does not do so at the terminal residue. Hence, it is used to release long carbohydrates from conjugated molecules. If an exoglycosidase were used, every monomer in the polymer would have to be removed, one by one from the chain, taking a long time. An endoglycosidase cleaves, giving a polymeric product.
PROTEIN-x1-x2-x3-x4-x5-x6-x7-x8-x9-x10-x11-...-xn
Mechanism Overview
The mechanism is an enzymatic hydrolysis that requires two critical molecules; a proton donor (most likely an acid) and a nucleophile(most likely a base).(1) The Endoglycosidases mechanism has two forms; an acid catalyzed protonation of the glycosidic oxygen yielding stereochemical retention at the anomeric carbon or an acid catalyzed protonation of the glycosidic oxygen with a concomitant attack of a water molecule activated by the base residue yielding a stereochemical inversion.(1)Both mechanisms exhibit the same distance between the proton donor and the glycosidic oxygen, situating the proton donor close enough to the glycosidic oxygen for hydrogen bonding.(1) It is the distance between the nucleophile and the anomeric carbon where the two mechanisms begin to diverge. Because the inversion mechanism must accommodate enough space for the water molecule, the nucleophile is situated further away from the anomeric carbon. In the inversion mechanism, this distance is only 5.5 angstroms but increases to 10 angstroms in the retention mechanism. Furthermore, the inversion mechanism was found to proceed through a single displacement mechanism involving an oxocarbenium ion-like transition state. Due to the retention mechanism’s proximity between the two carboxyl groups, it goes through a double displacement mechanism that produces a covalent glycosyl-enzyme intermediate.(2-3)
A exoglycosidase would remove each carbohydrate monomer (x) one by one from the end, starting at xn, whereas and endogylcosidase can cut at any glycosidic bond (-) and may cleave after a signature 'link oligosaccharide' that links certain carbohydrates to certain proteins.
For more information on linkages to proteins see O- and N- linked glycoproteins.
Endoglycosidases examples
| Endoglycosidases | Ose | cleaved bound |
| Endoglycosidase D | . | . |
| Endoglycosidase F | Glc-Nac | Glc // Nac |
| Endoglycosidase F1 | . | . |
| Endoglycosidase F2 | Glc-Nac | Glc // Nac |
| Endoglycosidase H Endoglycosidase H The enzyme Endoglycosidase H The enzyme Endoglycosidase H The enzyme Endoglycosidase H (Endo-β-N-acetylglucosaminidase H, is a highly specific endoglycosidase which cleaves asparagine-linked mannose rich oligosaccharides, but not highly processed complex oligosaccharides from glycoproteins... |
diacetylchitobiose | Nac // asparagine |
| Nac: N-acétyl-glucosamine Ref: http://www.chups.jussieu.fr/polys/biochimie/SFbioch/POLY.Chp.13.11.html |
||
Refer to the Handbook of Endoglycosidases and Glycoamidases http://www.amazon.com/dp/084933618X by Noriko Takahashi
Applications and Potential Uses
There has been great potential shown in the use of endoglycosidase enzymes undergoing mutagenesis. This new mutated enzyme when exposed to the proper compounds will undergo oligosaccharide synthesis and will not hydrolyze the newly formed polymer chains.(13) This is an extremely useful tool, as oligosaccharides have a great potential for use as therapeutics. For example, globo H hexasacccharide will indicate cancer related malignant cell transformation in the breast, prostate and ovaries. (4)Endoglycosidases also has potential application in fighting autoimmune diseases such as arthritis and systemic lupus erythematosus. In 2008, a team of researchers demonstrated that injection of endgoglycosidase S “efficiently removes the IgG-associated sugar domain in vivo and interferes with autoantibody-mediated proinflammatory processes in a variety of autoimmune models.”(5) Clearly the manipulation and mutation of this enzyme holds great promise for being able to fight a variety of diseases in the body.