Glycosyl hydrolase family 20 (GH20) catalytic domain of N-acetyl-beta-D-glucosaminidase (GcnA, also known as BhsA) and related proteins. GcnA is an exoglucosidase which cleaves N-acetyl-beta-D-galactosamine (NAG) and N-acetyl-beta-D-galactosamine residues from 4-methylumbelliferylated (4MU) substrates, as well as cleaving NAG from chito-oligosaccharides (i.e. NAG polymers). In contrast, sulfated forms of the substrate are unable to be cleaved and act instead as mild competitive inhibitors. Additionally, the enzyme is known to be poisoned by several first-row transition metals as well as by mercury. GcnA forms a homodimer with subunits comprised of three domains, an N-terminal zincin-like domain, this central catalytic GH20 domain, and a C-terminal alpha helical domain. The GH20 hexosaminidases are thought to act via a catalytic mechanism in which the catalytic nucleophile is not provided by solvent or the enzyme, but by the substrate itself.

Beta-N-acetylhexosaminidases of glycosyl hydrolase family 20 (GH20) catalyze the removal of beta-1,4-linked N-acetyl-D-hexosamine residues from the non-reducing ends of N-acetyl-beta-D-hexosaminides including N-acetylglucosides and N-acetylgalactosides. These enzymes are broadly distributed in microorganisms, plants and animals, and play roles in various key physiological and pathological processes. These processes include cell structural integrity, energy storage, cellular signaling, fertilization, pathogen defense, viral penetration, the development of carcinomas, inflammatory events and lysosomal storage disorders. The GH20 enzymes include the eukaryotic beta-N-acetylhexosaminidases A and B, the bacterial chitobiases, dispersin B, and lacto-N-biosidase. The GH20 hexosaminidases are thought to act via a catalytic mechanism in which the catalytic nucleophile is not provided by the solvent or the enzyme, but by the substrate itself.

Glycosyl hydrolase family 20, catalytic domain. This domain has a TIM barrel fold.

Glycosyl hydrolase family 20 (GH20) catalytic domain of dispersin B (DspB), lacto-N-biosidase (LnbB) and related proteins. Dispersin B is a soluble beta-N-acetylglucosamidase found in bacteria that hydrolyzes the beta-1,6-linkages of PGA (poly-beta-(1,6)-N-acetylglucosamine), a major component of the extracellular polysaccharide matrix. Lacto-N-biosidase hydrolyzes lacto-N-biose (LNB) type I oligosaccharides at the nonreducing terminus to produce lacto-N-biose as part of the GNB/LNB (galacto-N-biose/lacto-N-biose I) degradation pathway. The lacto-N-biosidase from Bifidobacterium bifidum has this GH20 domain, a carbohydrate binding module 32, and a bacterial immunoglobulin-like domain 2, as well as a YSIRK signal peptide and a G5 membrane anchor at the N and C termini, respectively. The GH20 hexosaminidases are thought to act via a catalytic mechanism in which the catalytic nucleophile is not provided by solvent or the enzyme, but by the substrate itself.

A functionally uncharacterized subgroup of the Glycosyl hydrolase family 20 (GH20) catalytic domain found in proteins similar to the chitobiase of Serratia marcescens, a beta-N-1,4-acetylhexosaminidase that hydrolyzes the beta-1,4-glycosidic linkages in oligomers derived from chitin. Chitin is degraded by a two step process: i) a chitinase hydrolyzes the chitin to oligosaccharides and disaccharides such as di-N-acetyl-D-glucosamine and chitobiose, ii) chitobiase then further degrades these oligomers into monomers. This subgroup lacks the C-terminal PKD (polycystic kidney disease I)-like domain found in the chitobiases. The GH20 hexosaminidases are thought to act via a catalytic mechanism in which the catalytic nucleophile is not provided by solvent or the enzyme, but by the substrate itself.

crystalstructure of a beta-N-acetylhexosaminidase [Akkermansia muciniphila ATCC BAA-835],6JEA_A crystal structure of a beta-N-acetylhexosaminidase [Akkermansia muciniphila ATCC BAA-835],6JEB_A crystal structure of a beta-N-acetylhexosaminidase [Akkermansia muciniphila ATCC BAA-835]

GH20C,Beta-hexosaminidase from Streptococcus pneumoniae in complex with PUGNAc [Streptococcus pneumoniae TIGR4]

GH20C,Beta-hexosaminidase from Streptococcus pneumoniae in complex with Gal-PUGNAc [Streptococcus pneumoniae TIGR4],5A6A_A GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with NGT [Streptococcus pneumoniae TIGR4],5A6A_B GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with NGT [Streptococcus pneumoniae TIGR4],5A6J_A GH20C, Beta-hexosaminidase from Streptococcus pneumoniae [Streptococcus pneumoniae TIGR4],5A6J_B GH20C, Beta-hexosaminidase from Streptococcus pneumoniae [Streptococcus pneumoniae TIGR4],5A6J_C GH20C, Beta-hexosaminidase from Streptococcus pneumoniae [Streptococcus pneumoniae TIGR4],5A6J_D GH20C, Beta-hexosaminidase from Streptococcus pneumoniae [Streptococcus pneumoniae TIGR4],5A6K_A GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with Gal-NGT [Streptococcus pneumoniae TIGR4],5A6K_B GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with Gal-NGT [Streptococcus pneumoniae TIGR4],5AC5_A GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with GlcNAc [Streptococcus pneumoniae TIGR4],5AC5_B GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with GlcNAc [Streptococcus pneumoniae TIGR4]

GH20C,Beta-hexosaminidase from Streptococcus pneumoniae in complex with PUGNAc [Streptococcus pneumoniae TIGR4],5A6B_B GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with PUGNAc [Streptococcus pneumoniae TIGR4],5A6B_C GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with PUGNAc [Streptococcus pneumoniae TIGR4]

GH20C,Beta-hexosaminidase from Streptococcus pneumoniae in complex with GalNAc [Streptococcus pneumoniae TIGR4],5AC4_B GH20C, Beta-hexosaminidase from Streptococcus pneumoniae in complex with GalNAc [Streptococcus pneumoniae TIGR4]

Hexosaminidase D OS=Mus musculus OX=10090 GN=Hexd PE=1 SV=1

Hexosaminidase D OS=Homo sapiens OX=9606 GN=HEXD PE=1 SV=3

Hexosaminidase D OS=Bos taurus OX=9913 GN=HEXD PE=2 SV=2

Beta-hexosaminidase Amuc_2018 OS=Akkermansia muciniphila (strain ATCC BAA-835 / DSM 22959 / JCM 33894 / BCRC 81048 / CCUG 64013 / CIP 107961 / Muc) OX=349741 GN=Amuc_2018 PE=1 SV=1