The Tetramer Structure of the Glycoside Hydrolase Family 27 α-Galactosidase I fromUmbelopsis vinacea

The crystal structure of Umbelopsis vinacea alpha-galactosidase I, which belongs to glycoside hydrolase family 27, was determined at 2.0 A resolution. The monomer structure was well conserved with those of glycoside hydrolase family 27 enzymes. The biological tetramer structure of this enzyme was constructed by the crystallographic 4-fold symmetry, and tetramerization appeared to be caused by three inserted peptides that were involved in the tetramer interface. The quaternary structure indicated that the substrate specificity of this enzyme might be related to the tetramer formation. Three N-glycosylated sugar chains were observed, and their structures were found to be of the high-mannose type.