We describe a PS4 variant polypeptide derivable from a parent polypeptide having non-maltogenic exoamylase activity, in which the PS4 variant polypeptide comprises an amino acid substitution at position 307 to lysine (K) or arginine (R), with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1. Preferably, the PS4 variant polypeptide further comprises an amino acid substitution at position 70, preferably G70D. The amino acid at positions 272 and 303 of the sequence of the are preferably histidine (H) and glycine (G).