Glycoside hydrolase

[1][2] They are extremely common enzymes, with roles in nature including degradation of biomass such as cellulose (cellulase), hemicellulose, and starch (amylase), in anti-bacterial defense strategies (e.g., lysozyme), in pathogenesis mechanisms (e.g., viral neuraminidases) and in normal cellular function (e.g., trimming mannosidases involved in N-linked glycoprotein biosynthesis).

One of the important occurrences of glycoside hydrolases in bacteria is the enzyme beta-galactosidase (LacZ), which is involved in regulation of expression of the lac operon in E. coli.

Glycoside hydrolases are found in the intestinal tract and in saliva where they degrade complex carbohydrates such as lactose, starch, sucrose and trehalose.

[7][11] The database provides a series of regularly updated sequence based classification that allow reliable prediction of mechanism (retaining/inverting), active site residues and possible substrates.

Recent progress in glycosidase sequence analysis and 3D structure comparison has allowed the proposal of an extended hierarchical classification of the glycoside hydrolases.

[15] An alternative mechanism for hydrolysis with retention of stereochemistry can occur that proceeds through a nucleophilic residue that is bound to the substrate, rather than being attached to the enzyme.

[17] These enzymes have a variety of uses including degradation of plant materials (e.g., cellulases for degrading cellulose to glucose, which can be used for ethanol production), in the food industry (invertase for manufacture of invert sugar, amylase for production of maltodextrins), and in the paper and pulp industry (xylanases for removing hemicelluloses from paper pulp).

Cellulases are added to detergents for the washing of cotton fabrics and assist in the maintenance of colours through removing microfibres that are raised from the surface of threads during wear.

Various glycoside hydrolases have shown efficacy in degrading matrix polysaccharides within the extracellular polymeric substance (EPS) of microbial biofilms.

[18] Medically, biofilms afford infectious microorganisms a variety of advantages over their planktonic, fre-floating counterparts, including greatly increased tolerances to antimicrobial agents and the host immune system.

For example, a combination of alpha-amylase and cellulase was shown to degrade polymicrobial bacterial biofilms from both in vitro and in vivo sources, and increase antibiotic effectiveness against them.