The enzyme mannosyl-glycoprotein endo-β-''N''-acetylglucosaminidase (endoglycosidase H) () has

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 semitrivi ...

''glycopeptide-D-mannosyl-N⁴-(N-acetyl-D-glucosaminyl)2-asparagine 1,4-N-acetyl-β-glucosaminohydrolase''. It is a highly specific endoglycosidase 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 (; ) is a saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars). Oligosaccharides can have many functions including cell recognition and cell adhesion. They are normally presen ...

, but not highly processed complex oligosaccharides from

glycoproteins Glycoproteins are proteins which contain oligosaccharide (sugar) 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 a ...

. It is used for research purposes to deglycosylate glycoproteins and to monitor intracellular protein trafficking through the

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

Structure and activity

Endoglycosidase H is isolated from '' Streptomyces plicatus'' 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 ...

''. Its

molecular mass The molecular mass () is the mass of a given molecule, often expressed in units of daltons (Da). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The derived quan ...

is 29 kDa. 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 (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 is commonly used by cell biologists to monitor

posttranslational modification In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis. PTMs may involve enzymes or occur spontaneously. Proteins are created by ribosomes, which translate mRNA ...

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 Cell (biology), cells. Part of the endomembrane system in the cytoplasm, it protein targeting, packages proteins ...

. Most proteins destined for the cell surface are translated by

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

into the rough

endoplasmic reticulum The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryote, eukaryotic cell, and has many other important functions such as protein folding. The word endoplasmic means "within the cytoplasm", and reticulum is Latin for ...

(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. It is this oligosaccharide molecule which is modified by a series of enzymes as the protein moves through the different compartments of the

. Endoglycosidase H is able to cleave each structure of this oligosaccharide as it is processed until the enzyme Golgi α-mannosidase II removes two

mannose Mannose is a sugar with the formula , which sometimes is abbreviated Man. It is one of the monomers of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylatio ...

subunits. Since all later oligosaccharide structures are resistant to cleavage by endoglycosidase H 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

Endoglycosidases 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