Glycosidases: Functions, Families and Folds

Abstract

Based in part on the previous version of this eLS article ' Glycosidases: Functions, Families and Folds' (2007) by Susan M Hancock and Stephen G Withers.Glycosidases catalyse the hydrolysis of glycosidic linkages, thereby degrading oligosaccharides and glycoconjugates, the structurally most diverse class of biopolymers. These efficient and highly specific catalysts play important roles in biological processes thus a detailed knowledge of glycosidase function is invaluable for understanding and controlling diseases and for industrial applications. The classification of this huge class of enzymes into families on the basis of amino acid sequence has provided a highly valuable tool for the analysis of structure-function relationships. Furthermore, the steady increase in three-dimensional structural information is revealing further evolutionary relationships between glycosidase families. In addition to the majority of glycosidases that act via the classical Koshland mechanisms, a growing number of such enzymes that use unusual mechanisms are being uncovered. This confluence of bioinformatics, structural and mechanistic studies has greatly advanced glycosidase engineering and the development of specific glycosidase inhibitors.

Nucleation of stable superconductivity in YBCO-films

“…(3.6)) and from the slowing down of τ −1 (Eq.(3.5)). The results shown in Fig.6 clearly demonstrate significant changes through the defects, except for B < 10mT to be considered elsewhere [18]. We find that the irradiation reduces Field dependence of the critical exponents ν and z determining the divergences of the correlation length and the relaxation times associated with the transition to generic superconductivity.…”

“…vortex-loop model. Additional support for the dominance of these phase fluctuations comes from the observation [18] that the relevant temperature variable, which described the critical behaviour up to vortex densities B = 19 T, is given by t = |T − T g (B)|/(T 0 − T ) (Eq.(3.5). Such behaviour emerges from the temperature variation of the coupling energy between the phases in the 3D-XY Hamiltonian [22,26].…”

A comprehensive overview of substrate specificity of glycoside hydrolases and transporters in the small intestine

“…The hydrolysis of the glycosidic bond is catalyzed by the carboxylic acid moieties of two amino acid residues of the enzyme: a general acid (proton donor) and a nucleophile/base. Depending on the arrangement of these groups hydrolysis of the glycosidic bond occurs with retention or inversion of the anomeric configuration [21][22][23]. MGAM and SI hydrolyze α-glucosides with retention of configuration ( Fig.…”

“…A classification has been made into glycosyl hydrolase (GH) families (145 families to date) depending on the amino acid sequence similarities and these can be further classified into groups (reported as clans) by similarities in folds and catalytic mechanism (see the Carbohydrate Active enZYme or CAZY data set https ://www.cazy.org) [20,22]. In addition, in this review the sub-site nomenclature proposed by Davies et al for glycosyl hydrolase binding sites is adopted, where n represents the reducing end of the carbohydrate chain, − n represents the non-reducing end and cleavage occurs between the − 1 and + 1 binding sites [28].…”

Metabolismo de fucose, alpha-L-fucosidases e fucosiltransferases: Caracterização enzimática, mecanismo de catálise e papel fisiológico.

“…Due to that, enzymes that process carbohydrates have acquired their specificity through structural differences and evolved from a limited number of ancestors (2). Among the bacterial α-L-fucosidases, the main species studied is the α-Lfucosidase from the thermophilic bacteria Thermotoga maritima (TmFuc), which was the first α-L-fucosidase to be crystallized (24).…”