AtFXG1, an Arabidopsis Gene Encoding α-l-Fucosidase Active against Fucosylated Xyloglucan Oligosaccharides

Abstract

Abstract An α-l-fucosidase (EC 3.2.1.51) able to release the t-fucosyl residue from the side chain of xyloglucan oligosaccharides has been detected in the leaves of Arabidopsis plants. Moreover, an α-l-fucosidase with similar substrate specificity was purified from cabbage (Brassica oleracea) leaves to render a single band on SDS-PAGE. Two peptide sequences were obtained from this protein band, and they were used to identify an Arabidopsis gene coding for an α-fucosidase that we propose to call AtFXG1. In addition, an Arabidopsis gene with homology with known α-l-fucosidases has been also found, and we proposed to name it as AtFUC1. Both AtFXG1 andATFUC1 were heterologously expressed in Pichia pastoris cells and the α-l-fucosidase activities secreted to the culture medium. The α-l-fucosidase encoded by AtFXG1 was active against the oligosaccharides from xyloglucan XXFG as well as against 2′-fucosyl-lactitol but not againstp-nitrophenyl-α-l-fucopyranoside. However, the AtFUC1 heterologously expressed was active only against 2′-fucosyl-lactitol. Thus, the former must be related to xyloglucan metabolism.