Abstract: Ligase mutants of the following (1), (2), or (3): (1) a ligase mutant comprising an amino acid sequence showing 95% or more identity to the amino acid sequence of SEQ ID NO: 1, and having a nucleic acid-linking activity; (2) a ligase mutant comprising an amino acid sequence showing 90% or more identity to the amino acid sequence of SEQ ID NO: 2, and having a nucleic acid-linking activity; or (3) a ligase mutant comprising an amino acid sequence showing 97% or more identity to the amino acid sequence of SEQ ID NO: 3, and having a nucleic acid-linking activity, have excellent properties.

Abstract: Formation of a modified oligonucleotide by treating four or more oligonucleotide raw material fragments in total in the presence of an oligonucleotide ligase; the four or more oligonucleotide raw material fragments in total corresponding to oligonucleotide raw material fragments that are obtained by dividing the modified oligonucleotide at a fragment linking site that satisfies following conditions (i) to (v): (i) one or more fragment linking sites are present in the complementary portion in each strand side, and two or more fragment linking sites in total are present in the modified oligonucleotide; (ii) when the modified oligonucleotide is divided at the fragment linking site, a sticky end is formed in the complementary portion, in which the sticky end has 1 to 10 nucleotide length; (iii) at least one oligonucleotide raw material fragment has a modified nucleotide; (iv) four oligonucleotide raw material fragments out of the four or more oligonucleotide raw material fragments in total include the complementa

Abstract: Ligase mutants of the following (1), (2), or (3): (1) a ligase mutant comprising an amino acid sequence showing 95% or more identity to the amino acid sequence of SEQ ID NO: 1, and having a nucleic acid-linking activity; (2) a ligase mutant comprising an amino acid sequence showing 90% or more identity to the amino acid sequence of SEQ ID NO: 2, and having a nucleic acid-linking activity; or (3) a ligase mutant comprising an amino acid sequence showing 97% or more identity to the amino acid sequence of SEQ ID NO: 3, and having a nucleic acid-linking activity, have excellent properties.