A subgroup of the Glycosyl hydrolase family 20 (GH20) catalytic domain found in proteins similar to the N-acetylhexosaminidase from Streptomyces plicatus (SpHex). SpHex catalyzes the hydrolysis of N-acetyl-beta-hexosaminides. An Asp residue within the active site plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state. 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. Proteins belonging to this subgroup lack the C-terminal PKD (polycystic kidney disease I)-like domain found in the chitobiases.
Structure:1M01_A; Streptomyces plicatus Beta-hexosaminidase bound with product (GlcNAc), contacts at 3.5A. N-acetyl-D-glucosamine
Comment:For 1M01_A, the most C-terminal active site Asp residue plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state.
Jiyao W et al.(2023). "The conserved domain database in 2023.",