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.

The chitobiase of Serratia marcescens is a beta-N-1,4-acetylhexosaminidase with a glycosyl hydrolase family 20 (GH20) domain 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 GH20 domain family includes an N-acetylglucosamidase (GlcNAcase A) from Pseudoalteromonas piscicida and an N-acetylhexosaminidase (SpHex) from Streptomyces plicatus. SpHex 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.

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

Beta-N-acetylhexosaminidases 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. The hexA and hexB genes encode the alpha- and beta-subunits of the two major beta-N-acetylhexosaminidase isoenzymes, N-acetyl-beta-D-hexosaminidase A (HexA) and beta-N-acetylhexosaminidase B (HexB). Both the alpha and the beta catalytic subunits have a TIM-barrel fold and belong to the glycosyl hydrolase family 20 (GH20). The HexA enzyme is a heterodimer containing one alpha and one beta subunit while the HexB enzyme is a homodimer containing two beta-subunits. Hexosaminidase mutations cause an inability to properly hydrolyze certain sphingolipids which accumulate in lysosomes within the brain, resulting in the lipid storage disorders Tay-Sachs and Sandhoff. Mutations in the alpha subunit cause in a deficiency in the HexA enzyme and result in Tay-Sachs, mutations in the beta-subunit cause in a deficiency in both HexA and HexB enzymes and result in Sandhoff disease. In both disorders GM(2) gangliosides accumulate in lysosomes. 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.

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

ChainA, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron],7DVB_B Chain B, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron],7DVB_C Chain C, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron],7DVB_D Chain D, Beta-N-acetylhexosaminidase [Bacteroides thetaiotaomicron]

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]

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]

Beta-N-acetylhexosaminidase OS=Cellulomonas fimi OX=1708 GN=hex20 PE=1 SV=1

Beta-hexosaminidase OS=Vibrio furnissii OX=29494 GN=exoI PE=1 SV=1

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_0868 OS=Akkermansia muciniphila (strain ATCC BAA-835 / DSM 22959 / JCM 33894 / BCRC 81048 / CCUG 64013 / CIP 107961 / Muc) OX=349741 GN=Amuc_0868 PE=1 SV=1

Beta-hexosaminidase OS=Porphyromonas gingivalis (strain ATCC BAA-308 / W83) OX=242619 GN=nahA PE=3 SV=2