The enzyme Endoglycosidase H (EC 3.2.1.96, Endo-β-N-acetylglucosaminidase H, N,N'-diacetylchitobiosyl beta-N-acetylglucosaminidase, mannosyl-glycoprotein endo-beta-N-acetylglucosamidase, di-N-acetylchitobiosyl beta-N-acetylglucosaminidase, endo-beta-acetylglucosaminidase, endo-beta-(1->4)-N-acetylglucosaminidase, mannosyl-glycoprotein 1,4-N-acetamidodeoxy-beta-D-glycohydrolase, endoglycosidase S, endo-N-acetyl-beta-D-glucosaminidase, endo-N-acetyl-beta-glucosaminidase, endo-beta-N-acetylglucosaminidase D, endo-beta-N-acetylglucosaminidase F, endo-beta-N-acetylglucosaminidase H, endo-beta-N-acetylglucosaminidase L, glycopeptide-D-mannosyl-4-N-(N-acetyl-D-glucosaminyl)2-asparagine 1,4-N-acetyl-beta-glucosaminohydrolase, endoglycosidase H) is an enzyme with systematic name glycopeptide-D-mannosyl-N4-(N-acetyl-D-glucosaminyl)2-asparagine 1,4-N-acetyl-beta-glucosaminohydrolase. It is a highly specific endoglycosidase which cleaves asparagine-linked mannose rich oligosaccharides, but not highly processed complex oligosaccharides from glycoproteins. It is used for research purposes to deglycosylate glycoproteins.

Endoglycosidase H is isolated from Streptomyces plicatus or Streptomyces griseus. Its molecular weight is 29 000 Daltons. The primary structure is described by Robbins 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.

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