Methods for enzymatic peptide ligation

A peptide ligase having peptide ligase activity and comprising or consisting of:

• (a) an amino acid sequence that shares at least 80% sequence identity with the amino acid sequence as set forth in SEQ ID NO:
• 1, provided that said peptide ligase comprises the amino acid sequence set forth in SEQ ID NO:
• 2 at the positions corresponding to residues 247-264 of SEQ ID NO:
• 1, and the amino acid at position 247 is alanine;
• or
• (b) a fragment of the amino acid sequence of (a) provided that said fragment comprises the amino acid sequence set forth in SEQ ID NO:
• 2 at the positions corresponding to residues 247-264 of SEQ ID NO:
• 1, and the amino acid at position 247 is alanine, and wherein the fragment is at least 150 amino acids in length;
• or
• (c) an amino acid sequence comprising the fragment of (b),
• wherein said peptide ligase is not the wild-type OaAEP1 having the amino acid sequence set forth in SEQ ID NO:
• 3 or butelase 1 having the amino acid sequence set forth in SEQ ID NO:
• 4.