Identification of key amino acid residues in Neisseria polysaccharea amylosucrase

Amylosucrase from Neisseria polysaccharea ea catalyzes the synthesis of an amylose-like polymer from sucrose, Sequence alignment revealed that it belo ngs to the glycoside hydrolase family 13, Site-directed mutagenesis enabled the identification of functionally important amino acid residues located a t the active center. Asp-294 is proposed to act as the catalytic nucleophil e and Glu-336 as general acid base catalyst in amylosucrase, The conserved Asp-401, His-195 and His-400 residues are critical for the enzymatic activi ty. These results provide strong support for the predicted close structural and functional relationship between the sucrose-glucosyltransferases and e nzymes of the a-amylase family, (C) 2000 Federation of European Biochemical Societies.