A method for producing imidazole dipeptide using a microorganism having imidazole dipeptide synthesis activity, the production method not including adding ATP, or including adding an amount of ATP that is less than the amount of imidazole dipeptide that is produced in terms of the number of moles, by utilizing an ATP supply system of the microorganism.

The present invention provides L-amino acid -ligase represented by sequence number 1 (SEQ ID NO. 1), which is a mutant protein including substitution of at least 1-3 amino acid residues of amino acid sequence of protein YwfE, with the substitution being at least one of an asparagine (N) residue of the 108th place from the N terminal being substituted with at least one of an alanine (A) residue, a glutamic acid (E) residue and a glutamine (Q) residue, an isoleucine (I) residue of the 112th place from the N terminal being substituted with a valine (V) residue, and a histidine (H) residue of the 378th place from the N terminal being substituted with at least one of a lysine (K) residue or an arginine (R) residue.