Modifications to lysine decarboxylase enzymes

A CadA variant polypeptide comprising at least one amino acid substitution at a lysine residue in a region corresponding to amino acids 276 to 509 as determined with reference to SEQ ID NO:

• 2, wherein the lysine residue occurs at the surface of the CadA variant polypeptide with the side chain oriented towards the external environment in a segment of the CadA variant polypeptide that lacks a defined secondary structure;
• and wherein the CadA variant polypeptide has at least 99% identity to any one of SEQ ID NOs:
• 2 to 5, wherein the substitution is at least at one of positions K320 and K325, wherein the substitution at position K320 is K320A/C/E/G/H/I/L/M/S/V/Y, and wherein the substitution at position K325 is K325C, wherein the lysine decarboxylase activity of the CadA variant polypeptide is improved compared to that of a wildtype CadA of one of SEQ ID NOs:
• 2 to 5.