Introducing transglycosylation activity in a liquefying alpha-amylase

By mutating Ala-289 by Phe or Tyr in the Bacillus stearothermophilus alpha-amylase, we induced this enzyme to perform alcoholytic reactions, a function not present in the wild-type enzyme. This residue was selected from homology analysis with neopullulanase, where the residue has been implicated in the control of transglycosylation [Kuriki et al. (1996) J. Biol. Chem. 271, 17321-173291. We made some inferences about the importance of electrostatic and geometrical modifications in the active site environment of the amylase to explain the behavior of the modified enzyme.