O-Glycosyl hydrolases (3.2.1.) are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families [1, 2]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.

This entry represents the catalytic TIM beta/alpha barrel common to many different families of glycosyl hydrolases found in all groups of organisms including viruses and Gene Transfer Agents (GTA) [3]. In the GTA of Rhodobacter capsulatus (Rhodopseudomonas capsulata) a glycosyl hydrolase domain is associated with ORFg15 (RCAP_rcc01698) [D5AU04, see Fig.1, in 4].

Structures have been determined for several proteins containing this glycosyl hydrolase domain, including family 13 glycosyl hydrolases (such as alpha-amylase) [5], beta-glycanases [6], family 1 glycosyl hydrolases (such as beta-glucosidase) [7], type II chitinases [8], 1,4-beta-N-acetylmuraminidases [9], and beta-N-acetylhexosaminidases [10].

1. Conserved catalytic machinery and the prediction of a common fold for several families of glycosyl hydrolases. Proc. Natl. Acad. Sci. U.S.A. 92, 7090-4
2. Structures and mechanisms of glycosyl hydrolases. Structure 3, 853-9
3. The gene transfer agent of Rhodobacter capsulatus and "constitutive transduction" in prokaryotes. Arch. Microbiol. 175, 241-9
4. Evolutionary implications of phylogenetic analyses of the gene transfer agent (GTA) of Rhodobacter capsulatus. J. Mol. Evol. 55, 534-43
5. Mechanistic analyses of catalysis in human pancreatic alpha-amylase: detailed kinetic and structural studies of mutants of three conserved carboxylic acids. Biochemistry 41, 4492-502
6. The mechanisms by which family 10 glycoside hydrolases bind decorated substrates. J. Biol. Chem. 279, 9597-605
7. High resolution X-ray crystallography shows that ascorbate is a cofactor for myrosinase and substitutes for the function of the catalytic base. J. Biol. Chem. 275, 39385-93
8. Expression and characterization of active site mutants of hevamine, a chitinase from the rubber tree Hevea brasiliensis. Eur. J. Biochem. 269, 893-901
9. A new lysozyme fold. Crystal structure of the muramidase from Streptomyces coelicolor at 1.65 A resolution. J. Biol. Chem. 276, 31994-9
10. Aspartate 313 in the Streptomyces plicatus hexosaminidase plays a critical role in substrate-assisted catalysis by orienting the 2-acetamido group and stabilizing the transition state. J. Biol. Chem. 277, 40055-65

O-Glycosyl hydrolases (Show more...

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