Evolution and biochemistry of family 4 glycosidases: implications for assigning enzyme function in sequence annotations.

ABSTRACT: Glycosyl hydrolase Family 4 (GH4) is exceptional among the 114 families in this enzyme superfamily. Members of GH4 exhibit unusual cofactor requirements for activity, and an essential cysteine residue is present at the active site. Of greatest significance is the fact that members of GH4 employ a unique catalytic mechanism for cleavage of the glycosidic bond. By phylogenetic analysis, and from available substrate specificities, we have assigned a majority of the enzymes of GH4 to five subgroups. Our classification revealed an unexpected relationship between substrate specificity and the presence, in each subgroup, of a motif of four amino acids that includes the active-site Cys residue: alpha-glucosidase, CHE(I/V); alpha-galactosidase, CHSV; alpha-glucuronidase, CHGx; 6-phospho-alpha-gluco

SUBMITTER: Hall BG 

PROVIDER: S-EPMC2767093 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature