Mutant beetle luciferase, gene, recombinant vector, transformant, and method for preparing mutant beetle luciferase

A mutant Photinus pyralis luciferase having mutations in an amino acid sequence of a wild-type Photinus pyralis luciferase, said mutations consisting of:

• (a) a mutation in which the amino acid corresponding to valine at position 288 in the amino acid sequence of the wild-type Photinus pyralis luciferase is isoleucine, leucine, or phenylalanine;
• and
• (b) a mutation in which the amino acid corresponding to glutamic acid at position 488 in the amino acid sequence of the wild-type Photinus pyralis luciferase is valine, alanine, serine, leucine, isoleucine or phenylalanine;
• and
• wherein a luminescence intensity of the mutant Photinus pyralis luciferase due to a luciferin-luciferase luminescence reaction in a 0.9% by mass sodium chloride solution is 50% or more with respect to that in a sodium chloride-free solution, and
• the luminescence intensity of the mutant Photinus pyralis luciferase due to the luciferin-luciferase luminescence reaction in the 0.9% by mass sodium chloride solution is greater than that of the wild-type Photinus pyralis luciferase.