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.

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.

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

ChainA, Beta-n-acetylhexosaminidase [Streptomyces plicatus],1HP5_A Chain A, Beta-n-acetylhexosaminidase [Streptomyces plicatus],1JAK_A Chain A, Beta-N-acetylhexosaminidase [Streptomyces plicatus],1M01_A Chain A, Beta-N-acetylhexosaminidase [Streptomyces plicatus],5FCZ_A Chain A, B-N-acetylhexosaminidase [Streptomyces plicatus],5FD0_A Chain A, B-N-acetylhexosaminidase [Streptomyces plicatus]

ChainA, Beta-N-acetylhexosaminidase [Streptomyces plicatus]

ChainA, Beta-N-acetylhexosaminidase [Streptomyces plicatus]

BT0459[Bacteroides thetaiotaomicron],6Q63_B BT0459 [Bacteroides thetaiotaomicron],6Q63_C BT0459 [Bacteroides thetaiotaomicron]

Structureand activity of the GH20 beta-N-acetylhexosaminidase from Streptomyces coelicolor A3(2) [Streptomyces coelicolor],4C7D_B Structure and activity of the GH20 beta-N-acetylhexosaminidase from Streptomyces coelicolor A3(2) [Streptomyces coelicolor],4C7F_A Structure and activity of the GH20 beta-N-acetylhexosaminidase from Streptomyces coelicolor A3(2) [Streptomyces coelicolor],4C7F_B Structure and activity of the GH20 beta-N-acetylhexosaminidase from Streptomyces coelicolor A3(2) [Streptomyces coelicolor]

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

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

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

Beta-hexosaminidase OS=Vibrio vulnificus OX=672 GN=hex PE=3 SV=1

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