Described is a PS4 variant polypeptide derivable from a polypeptide having amylase activity selected from: (a) a polypeptide comprising an amino acid mutation at each of positions 33, 34, 121, 134, 141, 146, 157, 161, 178, 179, 223, 229, 272, 303, 307, 309 and 334; (b) a polypeptide comprising an amino acid mutation at each of positions 33, 34, 121, 134, 141, 145, 146, 157, 178, 179, 223, 229, 272, 303, 307 and 334; (c) a polypeptide comprising an amino acid mutation at each of positions 33, 34, 121, 134, 141, 146, 157, 178, 179, 223, 229, 272, 303, 307, 309 and 334; and (d) a polypeptide comprising an amino acid mutation at each of positions 3, 33, 34, 70, 121, 134, 141, 146, 157, 178, 179, 223, 229, 272, 303, 307, 309 and 334; referring to the numbering of a Pseudomonas saccharophilia exoamylase shown as SEQ ID NO: 1.