| 摘要 |
We describe a food additive comprising a PS4 variant polypeptide, in which the PS4 variant polypeptide is derivable from a parent polypeptide having non-maltogenic exoamylase activity, in which the PS4 variant polypeptide comprises an amino acid substitution at position 121 with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1. The PS4 variant polypeptide may further comprise one or more further mutations at a position selected from the group consisting of: 161 and 223, preferably 161A, 223E and 223K, more preferably S161A, G223E and/or G223K, or the group consisting of: 134, 141, 157, 223, 307, 334, 33 and 34, preferably G134R, A141P, I157L, G223A, H307L, S334P, N33Y and D34N. In preferred embodiments, the PS4 variant polypeptide further comprises a mutation at position 87, preferably G87S, a mutation at position 178, preferably L178F, and/or a mutation at position 179, preferably A179T.
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