The enzyme endoglycosidase H () is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

with

systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivial ...

''glycopeptide-D-mannosyl-N4-(N-acetyl-D-glucosaminyl)2-asparagine 1,4-N-acetyl-beta-glucosaminohydrolase''. It is a highly specific

endoglycosidase An Endoglycosidase is an enzyme that releases oligosaccharides from glycoproteins or glycolipids. It may also cleave polysaccharide chains between residues that are not the terminal residue, although releasing oligosaccharides from conjugated pro ...

which cleaves

asparagine Asparagine (symbol Asn or N) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), an α-carboxylic acid group (which is in the depro ...

-linked mannose rich

oligosaccharides An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide polymer containing a small number (typically two to ten) of monosaccharides (simple sugar ...

, but not highly processed complex oligosaccharides from

glycoproteins Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...

. It is used for research purposes to deglycosylate glycoproteins and to monitor intracellular

protein trafficking :''This article deals with protein targeting in eukaryotes unless specified otherwise.'' Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations within or outside the c ...

through the

secretory pathway 440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical ...

Structure and activity

Endoglycosidase H is isolated from ''

Streptomyces plicatus ''Streptomyces rochei'' is a bacterium species from the genus of '' Streptomyces'' which has been isolated from soil in Russia.Deutsche Sammlung von Mikroorganismen und Zellkulturenbr>/ref> ''Streptomyces rochei'' produces borrelidin, butyrola ...

'' or ''

Streptomyces griseus ''Streptomyces griseus'' is a species of bacteria in the genus ''Streptomyces'' commonly found in soil. A few strains have been also reported from deep-sea sediments. It is a Gram-positive bacterium with high GC content. Along with most other s ...

''. Its

molecular weight A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...

is 29 000 Daltons. The primary structure was described by Robbins et al. in 1984. Endoglycosidase H cleaves the bond in the diacetylchitobiose core of the oligosaccharide between two

N-acetylglucosamine ''N''-Acetylglucosamine (GlcNAc) is an amide derivative of the monosaccharide glucose. It is a secondary amide between glucosamine and acetic acid. It is significant in several biological systems. It is part of a biopolymer in the bacterial ...

(GlcNAc) subunits directly proximal to the asparagine residue, generating a truncated sugar molecule with one N-acetylglucosamine residue remaining on the asparagine. It deglycosylates mannose glycoproteins, but the extent and rate of the deglycosylation depends to a high degree on the nature of the glycoproteins. The deglycosylation rate can be increased by denaturation of the glycoproteins (e.g., by carboxymethylation, sulfitolysis or by heating in the presence of sodium dodecyl sulfate). The addition of 0.1 M 2-mercaptoethanol highly increases enzyme activity against glycoproteins containing inter- or intra-molecular disulfide bridges, unlike detergents like Triton X-100, n- Octylglucoside, or zwitterionic detergents.

Biochemical applications

Endoglycosidase H (Endo H) is commonly used by cell biologists to monitor

posttranslational modification Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribosome ...

in the

Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ins ...

. Most proteins destined for the cell surface are

translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...

ribosomes Ribosomes ( ) are macromolecular machines, found within all cells, that perform biological protein synthesis (mRNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA (mRNA) molecules to f ...

into the rough

endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...

(ER) and translocated into the Golgi. Upon entering the ER a molecule containing 14 sugar subunits is linked ''en bloc'' to an asparagine in a selective manner by the enzyme

oligosaccharyl transferase Oligosaccharyltransferase or OST () is a membrane protein complex that transfers a 14-sugar oligosaccharide from dolichol to nascent protein. It is a type of glycosyltransferase. The sugar Glc3Man9GlcNAc2 (where Glc=Glucose, Man=Mannose, and Gl ...

. It is this oligosaccharide molecule which is modified by a series of enzymes as the protein moves through the different compartments of the Golgi apparatus. Endoglycosidase H is able to cleave each structure of this oligosaccharide as it is processed until the enzyme

Golgi alpha-mannosidase II Mannosyl-oligosaccharide 1,3-1,6-alpha-mannosidase (, ''mannosidase II'', ''exo-1,3-1,6-alpha-mannosidase'', ''alpha-D-mannosidase II'', ''alpha-mannosidase II'', ''alpha1-3,6-mannosidase'', ''GlcNAc transferase I-dependent alpha1,3 lpha1,6annosida ...

removes two

mannose Mannose is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation ...

subunits. Since all later oligosaccharide structures are resistant to Endo H cleavage the enzyme is widely used to report the extent of oligosaccharide processing a protein of interest has undergone.

References

External links

IUBMB Enzyme Nomenclature - EC 3.2.1.96

Close enzymes

Endoglycosidase An Endoglycosidase is an enzyme that releases oligosaccharides from glycoproteins or glycolipids. It may also cleave polysaccharide chains between residues that are not the terminal residue, although releasing oligosaccharides from conjugated pro ...

s F and D, cleave Glc-Nac PNGase F (Peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine_amidase) {{Portal bar, Biology, border=no EC 3.2.1