beta-Fructosidase superfamily: Homology with some alpha-L-arabinases and beta-D-xylosidases

Comparison of the amino acid sequences of four families of glycosyl hydrola ses reveals that they are homologous and have several common conserved regi ons. Two of these families contain beta -fructosidases (glycosyl hydrolase families GH32 and GH68) and the other two include alpha -L-arabinases and b eta -xylosidases (families GH43 and GH62). The latter two families are prop osed to be grouped together with the former two into the beta -fructosidase (furanosidase) superfamily. Several ORFs can be considered as a fifth fami ly of the superfamily on the basis of sequence similarity. It is shown for the first time that a glycosyl hydrolase superfamily can include enzymes wi th both inversion and retention mechanism of action. Composition of the act ive center for enzymes of the superfamily is discussed. Proteins 2001;42:66 -76. (C) 2000 Wiley-Liss, Inc.