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.

N-acetyl-beta-hexosaminidase [Carbohydrate transport and metabolism].

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 (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.

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

X-rayStructure of Flavobacterium johnsoniae chitobiase (FjGH20) [Flavobacterium johnsoniae UW101],6YHH_B X-ray Structure of Flavobacterium johnsoniae chitobiase (FjGH20) [Flavobacterium johnsoniae UW101]

Crystalstructure of GH20 Exo beta-N-Acetylglucosaminidase from Vibrio harveyi [Vibrio harveyi],6EZR_B Crystal structure of GH20 Exo beta-N-Acetylglucosaminidase from Vibrio harveyi [Vibrio harveyi],6EZS_A Crystal structure of GH20 Exo beta-N-Acetylglucosaminidase from Vibrio harveyi in complex with N-acetylglucosamine [Vibrio harveyi],6EZS_B Crystal structure of GH20 Exo beta-N-Acetylglucosaminidase from Vibrio harveyi in complex with N-acetylglucosamine [Vibrio harveyi],6K35_A Crystal structure of GH20 exo beta-N-acetylglucosaminidase from Vibrio harveyi in complex with NAG-thiazoline [Vibrio harveyi],6K35_B Crystal structure of GH20 exo beta-N-acetylglucosaminidase from Vibrio harveyi in complex with NAG-thiazoline [Vibrio harveyi]

Crystalstructure of GH20 Exo beta-N-Acetylglucosaminidase D437A inactive mutant from Vibrio harveyi [Vibrio harveyi],6EZT_B Crystal structure of GH20 Exo beta-N-Acetylglucosaminidase D437A inactive mutant from Vibrio harveyi [Vibrio harveyi]

Thecrystal structure of beta-N-acetylhexosaminidase from Bacteroides fragilis NCTC 9343 [Bacteroides fragilis NCTC 9343],4PYS_B The crystal structure of beta-N-acetylhexosaminidase from Bacteroides fragilis NCTC 9343 [Bacteroides fragilis NCTC 9343]

ChainA, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron],7DVA_A Chain A, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron],7DVA_B Chain B, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron]

Beta-hexosaminidase OS=Porphyromonas gingivalis (strain ATCC BAA-308 / W83) OX=242619 GN=nahA PE=3 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

Beta-hexosaminidase Amuc_2136 OS=Akkermansia muciniphila (strain ATCC BAA-835 / DSM 22959 / JCM 33894 / BCRC 81048 / CCUG 64013 / CIP 107961 / Muc) OX=349741 GN=Amuc_2136 PE=1 SV=1

Beta-hexosaminidase B OS=Pseudoalteromonas piscicida OX=43662 GN=nag096 PE=3 SV=1

Beta-hexosaminidase 1 OS=Coccidioides posadasii (strain RMSCC 757 / Silveira) OX=443226 GN=HEX1 PE=1 SV=1