InterPro domain: IPR002241

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) website.

Glycoside hydrolase family 27 GH27 comprises enzymes with several known activities; alpha-galactosidase ( 3.2.1.22 ); alpha-N-acetylgalactosaminidase ( 3.2.1.49 ); isomalto-dextranase ( 3.2.1.94 ).

Alpha-galactosidase (melibiase) catalyses the hydrolysis of melibiose into galactose and glucose [ 3 ]. In man, deficiency in the enzyme results in Fabry's disease (X-linked sphingolipidosis). Alpha-N-acetylgalactosaminidase catalyses the hydrolysis of terminal non-reducing N-acetyl-D-galactosamine residues in N-acetyl-alpha-D-galactosaminides [ 4 ]. Two conserved Asp residues may be involved in the catalytic mechanism in these enzymes. Deficiency in this enzyme results in Schindler and Kanzaki diseases.

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. Consideration of the evolution of the Saccharomyces cerevisiae MEL gene family on the basis of the nucleotide sequences of the genes and their flanking regions. Yeast 10, 1559-68
4. Human alpha-N-acetylgalactosaminidase-molecular cloning, nucleotide sequence, and expression of a full-length cDNA. Homology with human alpha-galactosidase A suggests evolution from a common ancestral gene. J. Biol. Chem. 265, 21859-66