The members of this family are similar to L-fucose isomerase expressed by E. coli (Swiss:P11552, EC:5.3.1.3). This enzyme corresponds to glucose-6-phosphate isomerase in glycolysis, and converts an aldo-hexose to a ketose to prepare it for aldol cleavage. The enzyme is a hexamer, with each subunit being wedge-shaped and composed of three domains. Both domains 1 and 2 contain central parallel beta-sheets with surrounding alpha helices. Domain 1 demonstrates the beta-alpha-beta-alpha- beta Rossman fold. The active centre is shared between pairs of subunits related along the molecular three-fold axis, with domains 2 and 3 from one subunit providing most of the substrate-contacting residues, and domain 1 from the adjacent subunit contributing some other residues [1].

1: Structure and mechanism of L-fucose isomerase from Escherichia coli. Seemann JE, Schulz GE; J Mol Biol 1997;273:256-268. PMID:9367760