Patent ID: 8137943

Claim:
A modified thermostable DNA ligase obtained by substituting a negatively charged amino acid in the amino acid sequence of a thermostable DNA ligase from thermophilic bacteria, hyperthermophilic bacteria, thermophilic archaea, or hyperthermophilic archaea, which corresponds to the aspartic acid at position 540 of the amino acid sequence of the thermostable DNA ligase from Pyrococcus furiosus shown in SEQ ID NO: 2, with a non-negatively charged amino acid, when the amino acid sequence of the thermostable DNA ligase is aligned with the amino acid sequence of SEQ ID NO: 2, wherein the thermostable DNA ligase from thermophilic bacteria, hyperthermophilic bacteria, thermophilic archaea, or hyperthermophilic archaea has sequence homology of 80% or higher with the amino acid sequence of SEQ ID NO: 2 and maintains an enzymatic activity at 70° C. or higher.