The present invention relates to:
an isolated or synthesized gene, which encodes a protein comprising the amino acid sequence represented by SEQ ID NO: 2,
an isolated or synthesized gene, which encodes a protein comprising an amino acid sequence comprising a deletion, substitution or addition of one or more amino acids with respect to the amino acid sequence represented by SEQ ID NO: 2 and being capable of regenerating luciferin,
an isolated or synthesized gene, which hybridizes with the complementary strand sequence of a DNA comprising the nucleotide sequence represented by SEQ ID NO: 1 under stringent conditions and encodes a protein capable of regenerating luciferin,
a recombinant DNA, which is characterized in that the above-described isolated or synthesized gene is inserted into a vector DNA,
a transformant or transductant comprising the above-described recombinant DNA, and
a process for producing a protein capable of regenerating luciferin, which is characterized in that the method comprises culturing the above-described transformant or transductant in a medium and collecting therefrom the protein capable of regenerating luciferin.