R-R2  (I)

wherein R1 is an amino acid selected from the group consisting of L-alanine, L-methionine, L-serine, β-alanine, L-threonine, glycine, L-cysteine and L-α-aminobutyric acid, and R² is an amino acid selected from the group consisting of L-alanine, L-glutamine, L-glutamic acid, glycine, L-valine, L-leucine, L-isoleucine, L-proline, L-phenylalanine, L-tryptophan, L-methionine, L-serine, L-threonine, L-cysteine, L-asparagine, L-tyrosine, L-lysine, L-arginine, L-histidine, L-aspartic acid, L-α-aminobutyric acid, βalanine, L-azaserine, L-theanine, L-4- hydroxyprol me, L-3-hydroxyproline, L-ornithine, L-citrulline and L-6-diazo-5-oxo-norleucine except L-alanyl-L-alanine, which comprises:

contacting, in an aqueous medium, at least two amino acids which may be the same or different, and a transformed microorganism comprising a polynucleotide encoding a protein selected from the group consisting of the following [1]to [3 ]:

[1]a protein comprising the amino acid sequence of SF0 ID NO:1;

[2]a protein comprising an amino acid sequence wherein 1 to 20 amino acid residues are deleted, substituted or added in the amino acid sequence of SEQ ID NO: 1 and catalyzing the synthesis of a dipeptide represented by formula (I); and

[3]a protein comprising an amino acid sequence which shows 98% or more similarity determined by BLAST program to the amino acid sequence of SEQ ID NO: 1 and catalyzes the synthesis of a dipeptide represented by formula (I);

forming and accumulating the dipeptide in the medium; and

recovering the dipeptide from the medium.